











UNITED STATES OF AMERICA. 





LETTERS 



ON 



MODERN AamOULTURE, 



BARON VON LIEBIG 



Edited by JOHN BLYTH, M.D., 

PEOFESSOE OF CHEMI8TKT, QUEEN'S COLLEGE, COEK. 



WITH ADDENTDA, 

BY A PRACTICAL AGRICULTURIST. 

EMBRACING YALUABLE SUGGESTIONS, ADAPTED TO THE WANTS OF 
AMERICAN FARMERS. 



NEW YORK: 

JOHN WILEY, 56 WALKER STREET. 

1859. 



Entered, according to Act of Congi-ess, in the year 1859, by 

JOHN WILEY, 

in the Clerk's Office of the District Court of the United States for the Southern 
District of New York. 



6"^^^ 



K. CRAIGHEAD, 

Stereotyper and Electrotyper, 

(Cavton ISiiiltiing, 

81, 83, and 85 Centre Street. 



TO 



HIS MAJESTY MAXIMILIAN II. 



KING OP BAVARIA. 



To the circle of men devoted to Art and Science, whom 
Your Majesty assembled around you last winter, for the 
purpose of obtaining from their discourses and their 
animated interchange of opinions a reflection of the intel- 
lectual movement of the age, I am in a great measure in- 
debted for the impulse which led to the researches to which 
these Letters on Modern Agriculture owe their origin. 

If, therefore, I venture, with the most profound respect, to 
dedicate to Your Majesty, who takes the same kind and 
active interest in the practical life of the nation and its wel- 
fare, as in science and its progress, this Work, which is in- 
tended to bring about the union of the natural sciences with 
agriculture, and to effect their beneficial co-operation, I do 



IV DEDICATION. 

SO in grateful remembrance of the active and powerful 
interest which Your Majesty has deigned to take in the 
labours of 

Your Majesty's 

Most obedient humble Servant, 

JUSTUS VON LIEBIG. 

Munich, April 2, 1859. 



EDITOE'S PEEFACE. 



These important and interesting Letters on "Modem 
Agriculture" are addressed by Baron Liebig, not to agri- 
culturists alone, but to every one wlio takes an interest in 
the welfare of bis country. 

The wants of an increasing population, and tbe danger 
of a possible stoppage, at any moment, of supplies drawn 
from foreign sources, make all feel a deep interest in tbe 
"discovery of tbe means of producing more bread and 
meat on a given surface." Landed proprietors, practical 
agriculturists, and men of science, bave all of late years 
devoted tbeir united energies to solve tbis important pro- 
blem. IVom tbe efforts of so many anxious labourers, as 
migbt be expected, a corresponding barvest of practical 
results has been obtained. Tbe autbor, wbo bas for years 
occupied bimself witb tbe elucidation of tbe laws of tbe 
nutrition of plants, passes in review, in these Letters, tbe 



vi editor's preface. 

mass of practical facts thus acquired, and by the light of 
science endeavours to give them their true import, and to 
deduce from them fundamental laws of general application 
in agriculture. 

It is not long since the humus theory occupied every 
work on agriculture, and the fertility of our fields was 
described as entirely dependent on the presence of this 
supposed valuable substance. The real nature of humus 
is, however, now understood, as well as the conditions 
under which alone it can prove valuable in the nutrition 
of plants. 

It is also now well known, that plants cannot grow and 
attain complete development, without the simultaneous 
action of atmospheric food and certain mineral elements, 
which are absolutely indispensable to their existence. The 
author has in these Letters shown, that no single element 
of these indispensable mineral matters possesses superiority 
over another, but that they are all of equal value to the 
life of a plant. Hence, if one of them be absent in the 
soil, a fully developed plant cannot be produced by the 
others, until the deficient element be supplied. But from 
the importance of this deficient element in a given case, 
we are not entitled to infer its equal efiiciency in other 
cases, where the same conditions may not exist ; — and yet, 



vu 



this fallacy lies at the root of many of the practical opera- 
tions of agriculture. 

The author points out the nature of this fallacy, and in 
the discussion of this subject, brings forward new and 
important facts connected with the nutrition of plants, and 
with the mode of action of some special manures. The 
mineral food of plants is shown by him to exist in the soil 
in two different states ; in the one, it is immediately avail- 
able ; in the other, it is not yet brought by decomposition 
into a condition for absorption by the roots. In every case 
the produce of a field and the duration of its fertility bear 
a fixed relation to the sum of the available food in the 
soil. Hence, if by mechanical or chemical means applied 
to the soil, we render the absorption of this food by plants 
more rapid, we thereby increase the amount of produce in 
a given time, and thus more quickly exhaust the stock. 
At the end of this given time the field will, for agricul- 
tural purposes, be unproductive, if the mineral matters 
removed by the crops be not restored. 

The author directs attention to the faxjt, that this funda- 
mental principle has been lost sight of in some of the 
systems of modern high farming, which have been based 
on the assumption that the available mineral food of plants 
in arable soils is inexhaustible. He urgently points out 



viii editor's preface. 

that in stimulating the productiveness of our fields by a 
system of high farming, without at the same time restoring 
all the mineral matter removed, the present occupiers of 
the land may rejoice in their abundant crops, but the in- 
evitable result of this system will be the ultimate exhaus- 
tion of the soil. 

The editor has endeavoured in this translation to convey 
to the reader as faithful a transcript as possible of Baron 
Liebig's views ; and accuracy has been farther insured by 
the revision of the proofs by the author. In conclusion, 
the editor begs to acknowledge the kind assistance of his 
friend Dr. Hofmann, from whom he has received many 
valuable suggestions whilst the sheets were passing through 
the press. 



JOHN" BLYTH. 



Queen's College, Cork, 
April 2, 1859. 



PREFACE. 



The state of matters to which the contents of these Let- 
ters refer, exists in reality in Germany alone ; and I should 
be taking an erroneous view of the actual position of Bri- 
tish agriculturists, were I to attribute to them the leading 
views entertained by Grerman and perhaps French agricul- 
turists. These letters must therefore be regarded as a mir- 
ror in which the scientific principles already established, 
and certain erroneous doctrines prevailing in practice are 
reflected side by side ; and each individual must be left to 
draw his own conclusions, on comparing his own acts with 
the standard thus furnished him. 

Upon the whole, English agriculture, as a rule, is based 
on the same spoliation system which exists elsewhere ; for 
though some certainly pursue a rational system, there are 
but too many who act otherwise. 

The remarks which I have made on writers on agricul- 
ture and on agricultural training schools, must be received, 
in like manner, with the same limitation. I am too little 
acquainted with the English agricultural institutions to 
pass judgment upon them, and my strictures can only be 



X PEEFACE. 

regarded as applying to those of Germany. With respect 
to the English agricultural chemists, I also readily ac- 
knowledge that Thos. Way, Professor Hodges, and others, 
have by their researches rendered the greatest service to 
agriculture. 

I cannot, however, concur in opinion with those who 
would base all progress in agriculture upon elementary 
analysis and on other useless chemical operations ; nor 
with those who forget that such progress results only from 
the investigation of scientific laws, and from a correct com- 
prehension of the facts observed, — things that cannot, like 
products in a manufactory, be procured wholesale by a 
mere outlay of capital and by a course of experiments. 

The great progress made in agriculture, since the end of 
last century, has been essentially confined to improvements 
in the practical part, by which I here mean to designate 
the technical operations of farming; but these improve- 
ments have paved the way for the new and higher develop- 
ment of the present day. It is in the nature of things, that 
in all technical pursuits, and more especially in agriculture, 
the perfecting of the practice should precede the effective 
application of scientific principles. So long as the man 
engaged in a technical pursuit finds that there is still ad- 
vantage to be derived from improvements in the manage- 
ment of his business, he will not trouble himself with other 
matters. But by improvements in the practice, or in the 
management of his business, everything desirable is not 
attained ; the practical operations in themselves give him 



PEEFACE. XI 

no insight into his own acts, nor a reliable standard for the 
value of his observations and experience : at last he will 
not permit himself to be swayed by the customary mode 
of proceeding. It is now that he turns to science to satisfy 
his requirements. 

As generally happens in the period of transition into a 
new state of things, a conflict has of late years been carried 
on between practice and science ; the former was unable 
to deal properly with the unwonted resources placed at its 
disposal by the latter ; and it is easy to account for the 
cause of this conflict. 

If, in fact, a person of the educated classes, who is not 
an agriculturist, were to peruse the agricultural works and 
journals that have appeared of late years, he would find 
that the preponderating majority of agricultural writers 
are quite agreed on this one point, that the views which I 
have put forward on agriculture, have no practical value, 
and must be looked upon as in part refuted. They main- 
tain that experience, which is older than science, has long 
since taught the practical man what is needful for him ; 
that the result proves his system of cultivation to be the 
best suited to existing circumstances ; and that his abun- 
dant and increasing crops are irrefragable proofs of the 
soundness of the views which guide his practice. 

These expressions and opinions are not generally appli- 
cable and valid ; they are not, however, groundless. The 
agricultural literature in which these views are put for- 
ward, exists in reality only for the class of thriving agri- 



XU PREFACE. 

culturists who are in a position to buy and possess agricul- 
tural manuals and journals ; and it is evident, that the 
literature will reflect the requirements, the wishes, and the 
practice of these agriculturists to whom it owes its exist- 
ence. It is not in the nature of things that it should be 
otherwise. As a rule, an agriculturist of this class is a 
producer of flesh and corn, and is generally possessed of a 
good property and plenty of capital ; his fields comprise 
meadows and arable land ; he keeps a large stock of cattle, 
produces plenty of farm-yard manure, and is not sparing 
in its use. If he happens to be short of manure, he has, at 
all events, money to buy guano. Chili-saltpetre, bone, earth, 
and rape-dust. He knows the value of farm-yard manure 
and of the supplementary manures just named, and how 
to use them to the best advantage. His steward attends to 
the rotation of crops which has been permanently fixed 
upon, and to the application of manure at the proper sea- 
son, — things which do not require the teachings of science ; 
he has to be guided, he tells you, by other circumstances 
which give him quite trouble enough. 

The wealthy landed proprietor is an educated man who 
has certain intellectual wants. Agricultural literature satis- 
fies these. The writer on agriculture endeavours to prove, 
by theoretical reasoning, the excellence of empirical prac- 
tice ; he defends the views of the practical man, and strives 
to invest them with the authority of science. Even if the 
explanations are at times in complete opposition to un- 
doubted truths, they have at all events this much in their 



PKEFACE. Xlll 

favour, viz., tliat the agriculturist believes them to be i:i 
accordance with his own experience ; and, indeed, the ob- 
ject of the writer does not extend beyond securing the 
satisfaction of the practical man, by showing what is termed 
the agreement of the practice of agriculture with the the- 
ory. Thus, for instance, in the production of corn and 
flesh, the alkalies in the farm-yard manure remain in the 
field, and in the progress of cultivation their quantity ra- 
ther increases than diminishes ; a restoration of these alka- 
lies is therefore not required, and would often be super- 
fluous. This circumstance, which arises from the kind of 
crop grown, the writer explains to the practical man to be 
the result of the nature of his soil ; he informs him that 
there is no necessity to restore the alkalies removed, be- 
cause his soil contains an inexhaustible quantity of them. 
It is true that this statement is directly opposed to all that 
Chemistry teaches ; but then it is a matter of indifference 
whether or not the soil is inexhaustible, if the main point 
be made out, viz., that there is no compensation of these 
matters required from without by purchase, &c. 

The writer on agriculture further informs the practical 
man, why guano and other manures used in aid of farm- 
yard manure are so beneficial. It is clear, he says, that all 
these matters contain in the nitrogen a constituent common 
to all of them ; and as the employment of each is attended 
by a similar result, viz., by a corresponding increase in the 
amount of produce, it is obvious that the effect must be 
attributed to one and the same cause in all. The practical 



XIV PKEFACE. 

man is told that in the corn and flesh produced on his land 
he removes nitrogen ; that the exhaustion of the soil is the 
consequence of this removal ; and that, of course, by re- 
placing this nitrogen, the productiveness of his fields is 
restored. To question the fact of the restoration of fertility 
to land by guano, bone-dust, or rape-dust, would be an act 
of great folly, for this fact is borne out by the experience 
of the practical man ; the latter, therefore, fully accepts the 
explanation offered, although there be in it only the merest 
semblance of truth. He is quite satisfied with the belief 
that his system of cultivation has been shown to rest on a 
rational and scientific basis; which, in reality, is not the 
case. 

Practical questions, such as the following : Why the 
after-effects of the above-mentioned manures are not uni- 
form with those of farm-yard manure, but differ so much 
from them : or why clover no longer grows on many 
fields ; or why peas, again, yield good crops on the same 
field only after long intervals : such questions as these, of 
course, do not engage the attention of the agricultural wri- 
ter. He speaks of such matters as if ordained by Nature ; 
which cannot be altered ; and for which the agriculturist 
must therefore make due allowance in his system of hus- 
bandry. But let the practical man only succeed — which, 
however, is not likely to be the case — in solving these 
questions, or in overcoming a difficulty which may have 
been placed in his way by the writer himself, and the lat- 
ter will at once proceed with right good will to prove to 



PKEFACE. XV 

him by a series of chemical analyses the intimate relation 
between theory and practice. 

These precepts of agricultural writers do no harm to the 
agriculturists for whom they are intended. These indi- 
viduals maintain their fields in a permanent state of fer- 
tility, by means of farm-yard manure, or by the purchase 
of guano and other manuring agents ; their simple system 
of cultivation affords no room for exhaustion of the soil. 
Whatever constituents they remove from the land in the 
form of corn and flesh, they replace completely, and even 
in excess. 

Although scientific doctrines play a very subordinate 
part in the system of cultivation pursued by these fortu- 
nate landed proprietors, inasmuch as their entire know- 
ledge consists in a few recipes which might be written upon 
a card ; yet it is for them that the most esteemed agricul- 
tural hand-books and manuals, and the greater number of 
the articles in agricultural journals are written ; it is for 
them that books on soils and manures are published, and 
enriched with stores of scientific learning from the domains 
of chemistry, physics, botany, and geognosy ; it is for their 
benefit that so many chemical analyses of corn and straw, 
hay and turnips, are made. They do not, indeed, read or 
understand all that is written, because, in fact, there is no 
intelligible meaning in it ; and they are quite aware that 
these rows of figures do not advance their business one 
hair's-breadth ; still they are delighted with all this parade 
of learning, on account of the seeming deep scientific basis 



XVI PREFACE. 

assigned thereby to agriculture, which they follow with so 
much ardour and profit. 

After the wealthy landed proprietors comes a second 
class of agriculturists, who possess land, but less capital 
than the former. They obtain good crops by the simple 
cultivation of their fields with farm-yard manure; they 
purchase but a small quantity of guano, or other manuring 
agents ; and trusting to the theory maintained by writers 
on agriculture, that their fields are inexhaustible in mineral 
matters, — which is intended to apply to a different system 
of cultivation from theirs, — they believe that there are no 
limits to the fertility of their land. As they have as yet 
observed no failure in the conditions of its fertility, they 
are of opinion that it will be time enough to devise means 
to meet the necessity when it occurs. 

These men also read the agricultural journals, and are 
quite satisfied in their own mind that the principles of 
science are not suited to their system of husbandry. They 
re-echo the opinions of the men of the first class, and are 
warm supporters of the precepts of the writers on agricul- 
ture, although the system of cultivation derived from these 
teachers brings their fields every year nearer that ruin to 
which they must inevitably come by following such a 
system. 

The resistance which science has met with on the part 
of practical men belonging to this class, is partly due to 
ignorance of its true princij)]es, partly to a wrong concep- 
tion and interpretation of the same. 



PKEFACE. XV 11 

If I have criticised the false views and opposition of 
these men, in purely chemical questions regarding the soil, 
manures, and the nutrition of plants, with a severity in- 
spired by sincere conviction, it must not be overlooked 
that they were the aggressors in the conflict. An attack 
of their views on my part would have been inexcusable ; 
for, with that simplicity which characterises those who pre- 
sume to j udge of things they do not understand, they have 
candidly avowed that chemistry and the natural sciences 
are branches of knowledge unknown to them. They are 
all, without exception, men deserving the esteem which 
they enjoy in their social relations, and whose feelings as 
individuals I could not have the most distant intention of 
wounding ; but when they step forward as supporters and 
propagators of precepts, which have nothing to recommend 
them beyond the fact that people have for half a century 
pursued a system of cultivation in conformity with them ; 
which are devoid of all rational basis, and are quite be- 
neath the present position of chemistry and the natural 
sciences, — precepts which must in process of time dry up 
the sources of prosperity of the agricultural population, — I 
should hold it to be a crime against the public interest 
were I to be restrained by any consideration for indi- 
viduals, or the position they may occupy, from laying bare 
the weakness and flimsiness of their arguments, and from 
exposing their total ignorance of the first principles of 
chemistry and the natural sciences. 

From want of a proper insight into their own pursuit, 



XVUl PKEFACE. 

these men are in their blindness the worst enemies ol 
science, the objects of which they do not comprehend. 

The scientific questions connected with agriculture aro, 
in their consequences, of too great importance for any one 
to enter upon their discussion, before he has seriously con- 
sidered whether he really understands the subject. 

One of the most important objects of the practical man 
is to discover active manures, by the use of which barren 
fields may be made productive, and the produce of fertile 
fields be doubled ; but they will never be found, or only 
accidentally, by seeking them blindfold in an empirical 
manner. The practical man does not know that for years 
the study of small and apparently insignificant things must 
be pursued, before the mind is prepared to grasp questions 
of importance. 

The method followed by science m seeking out active 
manures is very different, much more toilsome, but more 
certain. It is rendered doubly difficult from the fact, that 
the man of science who adopts it has not only to combat 
the erroneous notions prevailing in the domain of practice, 
but also the errors of his own science, which have their 
influence over him, and may cause him at times to make a 
false step ; but he knows that the path leading to light is 
thorny and dark, and the perception of an error is in itself 
a victory. 

The prevailing agricultural literature has nothing in the 
shape of aid to offer to the small landed proprietor or far- 
mer ; or to him who possesses little or no capital, no good 



PREFACE. XIX 

arable land, no meadow, an insufficient stock of cattle, and, 
accordingly, little or no farm-yard manure ; and those who 
cultivate commercial plants, such as tobacco, hops, flax, 
hemp, or the vine, find in it no information, no insight 
into the nature of their pursuit, but only insufficient rules, 
suited to particular localities. 

Science should, however, be the common property of 
all ; it should bestow aid on all who require and seek it, 
and should increase the intellectual store of rich and poor 
who are sincerely striving after truth. 

From the preceding remarks may be gathered the rea- 
sons which have induced me to publish these letters on 
Modern Agriculture. I am desirous to make the educated 
men of the nation acquainted with the principles which 
have been established by chemistry in connection with the 
nutrition of plants, the conditions of the fertility of soils, 
and the causes of their exhaustion. Should I be fortunate 
enough to impress upon a wider circle the conviction of 
the value of these principles, and of their extreme import- 
ance in a national and economic point of view, I shall look 
upon one of the tasks of my life as accomplished. With 
the aid of the educated men to whom I address myself, 
success is, in my opinion, certain ; but without their assist- 
ance it appears to me to be impossible. 

As regards those agriculturists who oppose the teaching 
of science from ignorance of its objects, I hold it of the 
greatest importance to be unwearied in our efforts in direct- 
ing their attention to the facts upon which scientific prin- 



XX PKEFACE. 

ciples rest ; for if we can but succeed in inducing them to 
reflect on the proofs of these principles, thej may be con- 
sidered as converts to the doctrines of science. 

The laws revealed by the study of the natural sciences 
will determine the future intellectual and material progress 
of countries and nations ; every individual is personally 
interested in the questions connected with their application. 

[n conclusion, I have to state that I have been indebted 
for a number of facts in Letters YI. and YII. to an excel- 
lent article in " Chambers's Information for the People," 
written, as I have since been informed, by K. Russell, Esq., 
Kilwhiss. 



CONTENTS 



LETTER I. 

The conflict between Science and Practical Agriculture — The foundation of 
Agriculture is experience — Progress founded on experience has its limits 
— The connection of Agriculture with Chemistry and the subsequent 
reaction — Progress in Agriculture must be based on the Inductive Method 
— False teachers of Agricultural Science — Practice based on the blind 
experience of others leads to error — The rejection of scientific teaching by- 
practical men due to their ignorance of the real object of Science — The 
solution by mere practical men of questions proposed by Agricultural 
Societies cannot advance Agriculture — The rejection of all scientific 
instruction by practical men only leads to self-deception 1 

LETTEK 11. 

Present profit is the leading principle of the prevailing system of Husbandry 
— This system is one of danger to Agriculture — GTeneral view of the 
Nutrition of Plants — Atmospheric and Mineral Food — The absolute neces- 
sity to Plants of aU the Constituents of their Mineral Food — Present 
views of the Nutrition of Plants erroneous — Rain water does not dissolve 
out the Mineral matters in the Soil — Remarkable absorbent power of Soils 
for the soluble Mineral Food of Plants, and particularly for Potash, Ammo- 
nia, and Phosphoric Acid — This power is limited, and varies with the Soil 
— Organic matter in the Soil materially modifies this power 19 

LETTER ni. 

Our cultivated plants do not receive their food from Solution — Roots of plants 
derive their Nourishment only from those portions of Soil absolutely in 
contact with them — This view supported by the composition of River, 
Well, and Drainage water — The Roots of plants must themselves exert 
some peculiar action in Nutrition — The Life of bnd-plants endangered by 



XXU CONTENTS. 

food when in Solution — In Water-plants the laws for the absorption of 
Food must differ from those of Land-plants — The Ash of duck- weed showa 
that plants have a Power of selecting their Food — Reason why mud from 
stagnant pools is a good Manure — Remarkable power for absorbiDg Mois- 
ture possessed by Soils — By absorption and evaporation of Moisture, the 
Soil is warmed or cooled — Great importance of this fact to Vegetation — 
The two Sources from which Moisture is absorbed by the Soil — Natural 
Law deduced from the above facts 30 

LETTER IV. 

The Belief in the value of Humus no longer exists ; its Action now ascertained 
— Effect of the Salts of Ammonia not dependent on their Nitrogen — The 
action of Nitrates like that of the Salts of Ammonia — Experiments with 
Nitrates and Chlorides — Experiments with Salts of Ammonia alone, and 
with the addition of Common Salt — Solubility of the Earthy Phosphates in 
solutions of Chlorides of Ammonium and of Sodium, and of Nitrate of Soda 
— Experiments with these Salts — Their Solvent Action similar to that of 
Carbonic Acid water — The Salts of Ammonia are decomposed in the soil ; 
their twofold action — Difference in the Comportment of Salts of Potash and 
of Soda in the Soil — Potash extracted by Sulphate of Ammonia from silicates 
— Application of the Action of Chili Saltpetre, Salts of Ammonia, and 
Chloride of Sodium to explain the increase of fertility in the soil, and the 
Nutrition of Plants 41 

LETTER Y. 

No free Ammonia in the SoU — The amount of Food obtained from the soil 
by plants is in proportion to the absorbent Root-surface — The early deve- 
lopment of Roots due to the accumulation of Nourishment in the surface 
soil — Estimations of the quantity of Ammonia in our cultivated fields — A 
deficient crop not due to the Absence of Ammonia in the soil — Experi- 
ments with salts of Ammonia; the crops only slightly increased thereby — 
Increase of produce due to accompanying Minerals —Experiments of Lawes 
and Kuhlmann with salts of Ammonia, &c. — The fertility of a field depend- 
ent on the sum of the Mineral matters in it — The activity of these Minerals 
increased within a given time by the Salts of Ammonia — The soil more 
rapidly exhausted by their use unless there is a restoration to it of the 
removed Mineral matters 51 

LETTER YL 

The Amount of Carbonic Acid and Ammonia in the Air — ^The Balance of 
Organic Life — The Absorption and Assimilation of Food differs in Perennial 



CONTENTS. XXlll 

and in Annual Plants— The mode of Growth of Perennial, Annual, and 
Meadow Plants — The quantity of Nitrogen in different Crops — Advantages 
of Nitrogenous Manures to Cereals is not in consequence of the failure of 
Nitrogen from Natural Sources — Organic and Nitrogenous Manures useful 
in Annual Plants with small absorbent Leaf and Root-surface — Effect of 
Nitrogenous Manures less marked in plants with large Leaf-surface — 
Supply of Ammonia in Manure not necessary to all Plants — Green Crops 
condense Ammonia from Natural Sources, and supply it in the excrement 
of animals to Corn-fields — The Nitrogen of Manures is thus indirectly 
obtained from the Air — The total quantity of Nitrogen from a manured 
Corn-field is not greater than from anommauured meadow, but more time 
is required by the latter to collect it — Explanation of the good effect of 
Nitrogenised Manures on Annual Plants with small Leaf and Root- 
surface 69 

LETTER YII. 

Salts of Ammonia increase the number of Roots and Leaves m the first period 
of the Growth of Plants ; hence the superior action of these salts ui Spring 
— Circumstances which modify the production of Leaves, Flowers, and Roots 
— Circumstances under which Nitrogenous and Concentrated Manures are 
useful — Causes of the failure of plants continuously grown on the same SoQ 
— Pood of plants when too concentrated often exerts a deleterious Chemical 
action — Provision in the Soil to prevent this action — Properties of Soils 
altered in cultivation by the removal of Mineral Matters from them, and by 
the increase of Organic Matters in them — The increase pf Organic Matter 
frequently a cause of Disease — Finger and Toe disease ; its cure — Excess 
of soluble Silica and of hurtful Organic Matter in soils removed by Lime — 
Noxious Organic Matters arising from the continuous growth of Perennial 
Plants on Meadows removed by Irrigation 80 

LETTER Vni. 

The food of Land Plants is not absorbed by the roots from Solution, but from 
the Soil directly in contact with them — Hence the necessity for a uniform 
distribution of the food of plants in the soil, and for the great Ramification 
of their Roots — A field with much mineral food may be comparatively 
unproductive if it is not thoroughly mixed with the Soil — The roots of a 
crop diminish the mineral food in those portions of the soQ in contact with 
them — Fertihty is restored to those portions by ploughing and other 
mechanical means, which mix the soU and allow the roots to ramify freely 
— Reason of the value of Green Manures — Estimation of amount of mine- 
ral food in the soil to produce different Remunerative Crops — Law of 
Exhaustion in soils for different crops — Action of organic remains in the 



XXIV CONTENTS. 

soil on the mineral constituents — Progress of diminution in Grain and Straw 
of cultivated crops, when the Ash Constituents are not restored to the soil, 
and when those of the straw alone are returned — Relation between the pro- 
duction of Leaves and of Grain — Relative proportions of mineral food 
required for Grain and for Root or Leaf-producing crops — The increase of 
Oi'ganic matter and Nitrogen in the soil by Green Crops, without the 
addition of mineral food, augments the produce of grain, but hastens the 
period of Exhaustion of the soil — Progress of the exhaustion of a soil by 
the cultivation of shallow and of deep rooting plants — The manner in which 
the Subsoil contributes to the prolongation of the fertility of land — 
Importance of the formation of large roots after germination — Exliausted 
fields in an agricultural sense — Fertility restored by manures — The nature 
of Manures — The part played by the Organic and Inorganic Matter of 
Manures — Farm-yard Manure 87 

LETTER IX. 

uonstant relation between the Sulphur and Nitrogen of Organic Compounds 
and the Alkaline Phosphates and Alkaline Earths of Cereals and Legu- 
minous plants — Mineral substances are as indispensable to the Life of 
Animals as to that of Plants — The amount of Phosphoric Acid and of 
Potash ascertained by analysis as existing in Soils is very small — The 
errors of Practical Teachers proved from the writings of Practical Agri- 
culturists — Fertility of land cannot be maintained by Nitrogenous and 
Carbonaceous Manures alone, but by the Restoration of the Ash Constitu- 
ents of Plants — Critical examination of the views of Walz, a practical 
teacher, on the Nutrition of Plants — The mineral food of plants in arable 
soils is not inexhaustible — The volatile and organic matters of Manures 
are not the most important — The nature of Guano and its active con- 
stituents 113 



LETTER X. 

The empirical agriculturist is a trader — The duties of the empirical and 
rational agriculturist — Views of Albrecht Block — Rotation of crops not un- 
important ; an underground crop is followed by a better cereal — Cropping 
of land without manure, and the removal of produce, cause exhaustion — 
The spoliation system of agriculture — Exhaustion of the lands in North 
America by this system — Exhaustion of the Minas Geraes fields — High 
farming is a more subtle system of spoliation of the soil — Mutual relation 
of clover, turnip, and corn crops ; and the results of removing from the 
lands the mineral constituents of these crops respectively — The German 
system of farming before the Thirty Years' "War — The German three-field 



CONTENTS. XXV 

system of rotation — Introduction of clover cultivation into Germany — 
Opposition to its introduction — False teaching in connection with the value 
of manures 138 

LETTER XL 

Ammonia is an element of food indispensable to Plants — Comparison of the 
action of Water and Ammonia — Ammonia is an element of food and a 
Solvent of Mineral Matters in the Soil — Ammonia alone, or its Salts, useless 
to Plants, without Mineral Food — Vast amount of Ammonia in arable Soils 
— The "Nitrogen" theory of Manures — The error of attributing the chief 
value of a Manure to its Nitrogen — The reason why the quantity of Nitro- 
gen in Guano and Excrements may be taken as a standard of their Agri- 
cultural value — Proper mode of Comparing the relative effects of Guano, 
Ground Bones, and Chili-saltpetre — The Loss of Fertilising matter in the 
Flesh and Grain carried to large towns; the constant loss of Phosphates in 
the Excrements of the inhabitants — The importation of Guano most 
inadequate to replace this loss — Superiority of Human Excrement over 
Guano as a Manure for Corn Fields — Tobacco, Potatoes, and Beet-root are 
more exhausting to a soil than Wheat — Injurious influence of extensive 
Cultivation of the Vine on the production of Corn and Wheat — Eifect of 
the Subdivision of the Land 165 

LETTER XIL 

Modern Agriculture has no history — The reason of this — The history of 
Roman Agriculture shows the existence of the spoliation system at that 
period — The works of Cato, Virgil, Varro, and Pliny inculcate, two thou- 
sand years ago, the same precepts that are now taught by many teachers 
of agriculture — Quotations from these writers, to show their opinions on 
the exhaustion of the ground ; on the different kinds of soils, and the 
modes of improving them ; on the selection of plants for the soils which 
are suitable for them ; on fallowing ; on the cultivation of green crops for 
manures ; on the different kinds of manure and their relative values, and 
modes of managing them — The various precepts inculcated of old only 
hastened the ruin of Roman agriculture 187 

LETTER XIIL 

The true object to be kept in view in establishing Scientific Principles — In 
scientific agriculture, "Manure," like the term "Phlogiston," has no longer 
a meaning — The cultivation of Green Crops for the purpose of keeping a 
stock of Cattle for manure is not necessary in the cultivation of land — The 
distinction between the Necessity and the Utility of keeping cattle — No 



XXVI CONTENTS. 

necessary connection exists between the production of Corn, and that oi 
JFlesh and Cheese — The fundamental principles of German Agriculture 
quite unknown in China — Chinese Agriculture — The manures employed 
by them — Great value set by Chinese on human excrements ; their mode 
of collecting and using them — Chinese compost — Their mode of sowing 
and transplanting wheat — Plants cultivated as green manure for rice fields 
— The lesson taught by the Chinese system of agriculture 196 

LETTER XIY. 

The law of Compensation is of universal application — Elementary information 
on Chemical subjects connected with Agriculture easily imparted — Im- 
portance of instructing youth at school in these fundamental truths — Theo- 
retical instructions should always precede Practical — The proper mode of 
instructing agriculturists in the Theory and Practice of Agriculture — The 
present constitution of Agricultural institutions very defective — The false 
position of Science in practical agriculture is the result of the teachings of 
these Schools — The demands made by Science on agriculturists are simple, 
and a knowledge of them cannot prove injurious — Science demands that 
agriculturists should test the Truths she advances — The truths in these 
Letters expressed by a Formula — The value of Guano first discovered by 
Science — The establishment of Reservoirs for animal excreta strongly 
recommended — Reliance to be placed upon such Excreta rather than on 
Guano — Chemistry can only help agriculturists after they have exhausted 
all the means at their disposal — Notes on supply of guano and on the 
agriculture of Tuscany 2 05 

APPENDIX 221 



LETTERS 



THEORETICAL AND PRACTICAL AGRICULTURK 



LETTER I. 



The conflict between Science and Practical Agriculture — The foundation of 
Agriculture is experience — Progress founded on experience has its limits 
— The connection of Agriculture with Chemistry and the subsequent 
reaction — Progress in Agriculture must be based on the Inductive Method 
— False teachers of Agricultural Science — Practice based on the bhnd 
experience of others leads to error — The rejection of scientific teaching by 
practical men due to their ignorance of the real object of Science — The 
solution by mere practical men of questions proposed by Agricultural 
Societies cannot advance Agriculture — The rejection of all scientific 
instruction by practical men only leads to self-deception. 

The present conflict between practical agriculture and 
scientific Chemistry, carried on by one party with some 
animosity and passion, perhaps to the ultimate advantage 
of the question at issue, might justly claim the attention 
of enlightened statesmen ; for it concerns the weightiest 
material interests and the fundamental prosperity of the 
state. The most urgent problem which the present day 
has to solve, is the discovery of the means of producing 
more bread and meat^ on a given surface, to supply the 
wants of a continually increasing population. The most 

Note. — The superior figures in the text refer to the treatment of the sub- 
jects in the Addenda. 

1 



2 THEOKETICAL AND PRACTICAL AGRICULTURE. 

important social questions are bound up in this problem, 
whicb science is expected to solve. 

Science has in her own way made the necessary prepara- 
tions for its solution, but her way does not please practical 
men. From them she has met with no support, but with 
opposition in almost eyery thing she has done. 

For the new building, which is to give room and shelter 
to all who will enter, science has levelled the ground ; she 
has drained it, and driven piles into the swamp, to insure 
a firm foundation ; she has indicated the best stone for use, 
and pointed out the fact that it is not found in all places, 
though the mortar may be had everywhere in abundance ; 
she has, finally, given the plan of the house ; but not one 
mason or carpenter, through whose assistance alone the 
house can be erected, has raised a hand to help her. 
Experience, they say, has been for centuries their guide, 
and must continue to be so for the future. In their eyes 
no views are admissible or possible, which contradict their 
views based on this experience. What has been regarded 
from time immemorial as true, must be true. The new 
plan is opposed to theirs, which is the best; neither the 
draining of the swampy ground, nor the driving of the 
piles, nor even the stones which are to be found every- 
where, are of any consequence ; only the mortar is wanting, 
on which every thing depends. 

Agriculture, like every technical pursuit, is based on 
experience, that is, on the perception by the senses of facts 
and phenomena ; and it has been enabled by experimental 
art to reach a certain stage of development. Simple 
observation shows a certain connection between the condi- 
tion of the soil and its fertility. Thus, a certain porosity 
and dark colour bespeak frequently a heavy wheat crop. 
Bat as all soils do not possess porosity and blackness, 
experimental art seeks out the means of communicating 



THEORETICAL AND PRACTICAL AGRICULTURE. 3 

tliese properties. It endeavours to produce, for a given 
object, a passing or a permanent connection between two 
facts ; it seeks to win from the soil a high return by this or 
that planij manure, or other means. 

Every object attainable by experimental art must be 
pursued with certain ideas, but it is immaterial whether 
those ideas be right or wrong. For if we seek an object 
without knowing the proper way to do so, each path taken 
by us is, for the time being, the right one. If, then, thou- 
sands of persons with the same intention strike out 
thousands of different courses, it will generally happen 
that something useful is discovered, although not precisely 
the object sought. In this way trades have been developed. 
It is almost incredible what can be done, and has, in fact, 
been accomplished in this way. 

The connection between two objects, such as the soil and 
manures, is known only through means of a third, viz., the 
amount of produce. For the practical man, " the matter- 
of-fact man," there exists no other connecting link. 

The exercise of a trade presupposes no intellectual 
labour; a knowledge of facts, and of their visible and 
manifest connection with each other, being quite sufficient 
for the purpose. The baker knows nothing about flour, 
leaven, or the influence of fermentation and heat ; the soap- 
boiler is ignorant of the nature of the alkaline lye, of fat, 
and of soap ; but both know that by taking certain steps 
bread or soap is produced. If the articles look well, they are 
said to have succeeded. In like manner, a few years ago, the 
agriculturist knew nothing about the soil, the atmosphere, 
or the action of the plough or of manures ; things with 
which he was daily occupied. 

The efforts of every tradesman are, as a matter of course, 
directed to his profits ; every improvement in his business 
has the increase of his income for its object. Hence the 



4: THEORETICAL AND PEACTICAL AGRICULTURE. 

baker regards the highest effort of his art to be the produc- 
tion of a white and weighty bread from inferior and bad- 
coloured flour ; and the soap-boiler aims at manufacturing 
from bad fatty matters a soap with good external aspect. 
The practical agriculturist, in the same way, endeavours 
to reap the richest harvest from the poorest soil with the 
least expenditure of labour and manure. In this petty 
aim is manifested the paltry principle of the small manu- 
facturer. 

The progress of every trade by mere empirical experi- 
ence, and also that of agriculture, has a limit. Every 
experimental method comes to an end when the senses are 
no longer sufficient for the perception of facts ; when no 
new circumstance is presented to the senses for perception ; 
when, in short, every thing has been tried, and the facts 
resulting from such trials have been adopted into the par- 
ticular art or trade. Further progress can then only be 
looked for, if hidden facts are sought out, the senses are 
sharpened for their perception, and the means of investiga- 
tion are improved. But such a course is not possible with- 
out reflection, without the mind also taking its share in the 
operation. 

It is long since agriculture has reached this point of its 
progress. As, however, in following out their own practical 
mode, agriculturists had never troubled themselves about 
the way or the means of discovering hidden facts ; it was 
evident that without the aid of Chemistry, — ^the science 
which communicates this knowledge, — they could never 
attain their end. Chemistry most readily responded to the 
call. In the verj outset the practical agriculturist was 
informed by the chemist that his conception of the words, 
azV, soil, manure, was indefinite and ambiguous ; that they 
had a fixed and definite meaning, and that it was only in 
this strictly defined form that they could be employed in 



THEORETICAL AND PRACTICAL AGRICULTURE. 5 

processes of reasoning. Chemistry thus elevated mere 
practical notions to the rank of scientific conceptions. 

The newly acquired conception of manure was accepted 
with enthusiasm by agriculturists, and they set themselves 
with zeal to work it. It was known that manure was the 
most important element in increasing a crop. It had been 
shown that the word " manure" was a collective term; that 
it consisted of parts, and that its activity depended on its 
constituents. The practical agriculturist now began to 
operate with the parts as he had done with the whole 
manure. But as a part can never replace a whole, so the 
results, by this mode of proceeding, did not answer his 
expectations. No progress was made. Enthusiasm began 
to cool, and reaction commenced. 

" It is utterly absurd," says Mr. Pusey (late President of 
the Agricultural Society of England), "to put any value on 
the doubtful precepts of Chemistry. It has done nothing 
for agriculture, with the exception of giving a receipt for 
increasing the efficacy of bones by the action of sulphuric 
acid, and of proposing to employ flax-water instead of 
liquid manure. We must keep to practice, for it alone is 
worthy of confidence." Every practical man in England, 
Germany, and France, quite agreed in this opinion. Che- 
mistry had done them no good ; it had not increased their 
crops, nor augmented their incomes. 

As if freed from a frightful night-mare, blind empirical 
practice again raised her head, and made new and extra- 
ordinary efforts to refute the conclusions drawn from scien- 
tific principles. The continued efforts of ten years have, 
however, shown that practice has only been moving in a 
circle, like a horse in a mill. More horses have been 
yoked; but as the beam was not lengthened, the circle 
has remained the same, only somewhat more trodden than 
formerly. 



6 THEORETICAL AND PRACTICAL AGRICULTURE. 

A new movement now occurred in agriculture. Science 
pointed out that tlie very facts destined to refute her doc- 
trines, exhibited the fullest proof of their soundness. Agri- 
culturists had themselves to blame for their want of success, 
by not taking the right path and by mistaking the nature 
and essence of science. It is not at all the province of 
science to seek out the means of increasing produce or 
augmenting incomes. She inquires not after what is profit- 
able ; this belongs to experimental art, with which she has 
been confounded. The business of science is to seek for 
causes, and like a light, to illuminate the surrounding dark- 
ness. Science confers poiver^ not money ; and power is the 
source oi riches and of poverty^ — of riches when it produces^ 
and of poverty when it destroys ; it is expended by %ise^ and 
renewed by supply. 

If agriculture is to arrive at results which are to be 
lasting, she must decide upon entering on that path which 
science has recognised to be the only trustworthy one to 
lead to a knowledge of hidden objects and their relations; 
This could be done without renouncing one of the facts 
acquired by experience. There is no lack of these, but 
agriculturists are at fault in their mode of comprehending 
them. They must, in the first place, desist from drawing 
hasty conclusions for special purposes from these facts, and 
only occupy themselves with investigating the proximate 
conditions of all the facts connected with the life and 
development of plants, the production of which is their 
object. From the favourable action of the constituent of a 
manure in one case, they must not at once infer its equally 
favourable action in another, in order to derive immediate 
profit from it ; but they ought, in the first place, to inquire 
into the reason of its good effects in the special case. 

Such investigations are in an agricultural point of view 
greatly facilitated by all the conditions of the incidents, or 



THEOKETICAL AND PRACTICAL AGRICULTURE. 7 

effects, or their proximate causes, being clearly perceptible 
by the senses, and palpably manifest if we know the proper 
way to proceed. 

The favourable action of a manure A is always dependent 
on certain physical conditions of the soil, and on the pre- 
sence of a second substance B, of a third C, of a fourth D, 
and so on. After investigating these different points, our 
conclusion must then be submitted to proof, which must 
show whether all the conditions have been considered 
together, and none overlooked. AYe must endeavour to 
produce the same effect in another soil, by the combination 
of all the conditions found. Should the result correspond 
with our expectations, and be equally favourable as in 
the first instance, we have made an extraordinary step in 
advance ; for from this special case we can now in all similar 
cases predict the like or unlike effect of the manure A. 
The effects will be like, in every instance in which we 
know that we have present the same conditions united in 
the same manner ; and unlike, when one of these is known 
to be wanting. 

The presence and united action of all the conditions of 
the effect observed, is designated by the term, a special law; 
because it refers to a special case, to a certain plant for 
instance. If this law holds good for superphosphate of 
lime and " turnips," it does not follow that it is equally true 
for "wheat." But a similar special law can be estabhshed 
for each manure, each plant ; and from these again general 
laws can be deduced, which express the conditions of the 
growth and development of all varieties of cereals^ all species 
of turnip and tuberous plants, &c. These connected general 
laws now receive the name of theory. 

It must be evident, even to the most limited under- 
standing, that there is nothing hypothetical in this pro- 
ceeding. It differs from blind experimental art, only in 



8 THEOKETICAL AND PEACTICAL AGRICULTUEE. 

being the result of thought and reflection. As the train of 
thoughts, on which the experiments are based, is carried 
out in a precise and fixed direction, this mode of proceeding 
has received the name of the inductive method. 

The world has been metamorphosed by the introduction 
of this method, which was unknown to antiquity. It is 
to this method that the present day is indebted for its 
peculiar characters. The Greeks and Komans possessed 
metaphysics and the fine arts as we do ; but the natural 
sciences, the offsprings of the inductive method, were 
unknown to them. To this method we owe the millions 
of wilHngand industrious slaves, whose labour costs no 
tears or groans. It has bestowed on Germany alone what 
is equivalent to from 700,000 to 800,000 horses, which, 
with untiring energy, and with the speed of the wind, 
bring from the most distant lands their various products to 
satisfy the wants of man ; and they need no hay, no corn 
to feed them. The fruitful land necessary to produce the 
food for this number of horses of flesh and blood, remains 
for the use of five to six millions of men, who can be main- 
tained on its surface. 

Conclusions deduced from this method of investigation, 
are evidently but the intellectual expressions for experi- 
ments and facts. The practical man who adopts this 
method of solving all useful questions, need entertain no 
dread of acquiring the reputation of a theorist, which he 
considers to be of a rather doubtful nature. He may rest 
assured that by no other means can he solve a single 
problem. He must first seek after the "why," and the 
" wherefore " will follow as a matter of course. 

It would be unjust to conceal the fact that, for more than 
half a century, agriculturists have directed all their efforts 
to gain an insight into the processes of husbandry. They 
have endeavoured to connect all its phenomena together by 



THEOKETICAL AND PRACTICAL AGRICULTURE. 9 

some intelligible bond, and to ascertain the relation and 
dependence of its scattered facts. 

Agriculture could not remain unaffected by the extra- 
ordinary progress of other trades depending on the action 
of natural forces. The natural sciences were even recog- 
nised to be the source of this progress. Wise and intelli- 
gent princes erected schools and institutions, for the express 
purpose of teaching the doctrines and truths of the natural 
sciences in connection with the practice of agriculture, of 
investigating the best modes of cultivation, and of widely 
spreading the knowledge of them. 

Agriculturists felt the necessity of accounting for their 
acts ; and the knowledge that they were doing the right thing 
in the right way, appeared to all indispensable to progress. 

If we open a recent hand-book of practical agriculture, 
we at once see the zeal with which this task has been per- 
formed. The effect of soils, manures, irrigation, drainage, 
and the action of each fertilising agent on individual classes 
of plants, are all brought into harmony and explained in 
the most beautiful manner. Everything seems in such 
works to have been investigated and ascertained ; no pro- 
cess is involved in obscurity ; and a certain feeling of pride 
seems to fill the breast of the teachers who have done so 
much to elevate agriculture to the rank of a science. 

But this is all sham^ without a single law or a single truthf^ 
" If there is a class of mind in the world which has a native 
antipathy to improvement, there is another and much more 
really mischievous, which seems ever destined to caricature 
it. . . . These are the blundering enthusiasts who dog 
the path of progressive truth, like distorting shadows, 
throwing her calm profile against walls, trees, and passing 
objects, in every variety of burlesque and ridiculous out- 

* The Chronicle of a Clay Farm, by TlaJi^Si.— Agricultural Gazette. 
1* 



10 THEORETICAL AND PRACTICAL AGRICULTURE 

line ; . . . exaggerating every account like street ne"v^ s- 
vendors ; dressed in the livery of science like a mon.-cey in 
regimentals, and understanding and appreciatig the lan- 
guage they talk at second-hand, as much as the organ- 
grinder does the opera tune that his winch works thread- 
bare. 

" Agriculture has had enough of this and something to 
spare. Counterfeits of every sort and shape have crowded 
at the heels of every improvement, every invention, every 
good suggestion, every new manure ; till art and science 
are well nigh ashamed of their own names, and are fain to 
wear smock-frocks for an incognito. The plague that has 
reached its height in the present decade, was beginning 
its infective process in the last of our nineteenth century." 

Agriculturists knew not that the explanation of the most 
trifling incident or process, or the discovery of the almost 
self-evident cause of an effect, costs much pains and cir- 
cumspection ; that in chemistry, for example, the simplest 
explanation of a single individual fact has been attained, 
only by persevering labour. They thought that to will^ 
was to obtain possession ; and they hence gave themselves 
up to the direction of those caricaturists of science who 
promised them success without any efforts on their part. 
They were well pleased with their sham scientific mode of 
proceeding, with which they were at home, and which cost 
them but little trouble. The language alone was new, but 
technical terms were soon learned. Each individual con- 
sidered himself as fully qualified to institute chemico- 
agricultural experiments ; and these were undertaken even 
by men who knew no more about chemistry than the 
student who considers that the distillation of a fluid is to 
be attained by simply placing it in the sun, or the other 
who asked the chemical assistant in a laboratory for a grater 
to pulverise a mineral. 



THEORETICAL AND PEACTICAL AGRICULTURE. 11 

Such men arrived at explanations in the simplest manner 
possible. If between two facts there existed a certain and 
unmistakeable connection, — such as for example, between 
irrigation and the increase of grass on a meadow, — these 
pseudo-scientific experimenters drew on their imaginations 
for the explanation of this connection. 

The causes of the effect produced were unknown. There 
was, however, an effect visible, and it must have a cause. 
The expounder began first by mystifying with a chemical 
hocus-pocus of analysis, the good-natured agriculturist 
thirsting after knowledge ; and when he had sufficiently con- 
fused the sound common sense of the latter by "unmeaning 
numbers and calculations, he quietly palmed off on him his 
explanation which he had ready prepared. 

The connection between two facts was not, however, 
always so palpable, as between irrigation and production 
of grass ; but our agricultural expounders were never at a 
loss. If they wished to show, for example, the connection 
existing between the exhaustion of the soil and the cultiva- 
tion of cereals^ they required only to call to their aid certain 
speculative views derived from experience. For such 
occasions they had always ready chiefly two famous theo- 
ries, viz., the ''bone earth" and the "nitrogen" theories. 
The latter has attained great celebrity in England, and in 
Grermany. too, it has found ardent supporters. 

There can be only one straight line between two points ; 
but billions of curved lines may connect them. Thousands 
of hypotheses may, in like manner, be propounded to 
explain the connection of two facts ; but there can be only 
one right theory. Every one will therefore understand 
that agriculture, by following the method described above, 
could never arrive at the right way of explaining her 
various facts. The popularity of this mode of proceeding 
arose from the circumstance that knowledge was not 



12 THEORETICAL AND PRACTICAL AGRICULTURE. 

required to practise it. Every agriculturist, in his own 
estimation, possessed the necessary qualifications for the 
purpose. He knew the facts, and his own experience was 
quite sufficient to connect them. But as the individual 
experience of each necessarily varied in many respects, it 
followed that each had his own peculiar theory for his pro- 
ceedings and his mode of viewing things. 

In reality these theories were but little regarded. The 
practical man kept to what had been tried, and acted upon 
it. If his neighbour made a successful trial, he imitated 
his example. This was his mode of making progress ; he 
knew no other. 

The practical agricultural system of instruction was a 
mere collection of different receipts suitable to known 
cases ; it was an olla podrida of facts, with theory as a kind 
of sauce to it. 

The agriculturist commencing his career became a prac 
tical man, and acquired reputation and honour somewhat 
like the so-called "green" Doctor of Offenbach on the 
Maine, who will perhaps still be recollected by the older 
inhabitants of this town. He was a Jewish physician of 
renown who was called in to all dangerous cases of illness 
in Frankfort, Hanau, and the neighbourhood; and his 
practice was not without success. Nature had given him 
a quick eye and fine powers of observation. His know- 
ledge was obtained in an hospital in which he acted as sick 
attendant. He used to accompany the physician through 
the sick wards, looked at the tongues and urine of the 
patients after him, felt their pulse, and superintended the 
orders about their diet. He copied the prescriptions regu- 
larly; marked them with a red cross when the patient 
recovered, and with a black one when he died. His sheets 
grew by degrees to the size of a book, and when nothing 
new presented itself to be added to it, he began in the first 



THEOEETICAL AND PEACTICAL AGRICULTUEE. 13 

instance to practise on a small scale, and then started on 
tbe full career of physician. He was skilled in diagnosis, 
and had his prescriptions for the various cases. Those 
with the red crosses came first ; and, if unsuccessful, then 
followed the black. In this way he acquired his own expe- 
rience. He was very orthodox, and on the Sabbath day 
would write no 'prescription, but would then dictate them 
in the apothecary's shop to the assistant. He commenced 
with '■'• Rrrrr'^ (this meant Recipe); " Tartemet^ two grains" 
(^. e. Tartar! emetici grana duo); Syralth {i. e. syrupus 
altheoe). He could not read his own prescriptions, but his 
fame as a practical physician was so established, that the 
regularly educated physicians in Offenbach could not suc- 
ceed in putting an end to his career, on the ground of his 
never having received a medical education. 

Agricultural practice is acquired in the present day 
exactly in the same way as the medical skill of the Offen- 
bach doctor. The young agriculturists become sick atten- 
dants in an agricultural hospital ; they copy the prescrip- 
tions, and when they depart for the purpose of beginning 
practice, the kindly directors send them on their way, with 
the substance of two years' earnest devotion to all the aux- 
iliary sciences summed up in an axiom, "Dung, Guano, 
and Bone-earth, you must not forget, gentlemen, are, and 
remain the soul of agriculture."* They knew this very 
well. They had been taught that no trust was to be put 
in chemistry or physics ; that food and drink keep body 
and soul together; and that beer, bread, and meat, are 
the soul of the handicraftsman. 

Under such circumstances, it cannot excite astonishment, 
that for more than sixteen years true science found no soil 
in agriculture for its development. The most exact indue- 

* See G-. Walz. Beleuchtung. p. 128. 



14 THEORETICAL AND PRACTICAL AGRICULTURE. 

tive conclusions were only regarded as hypotheses. It has 
ever been the case that when error sat enthroned, truth, 
like a felon, was kept bound in chains. What arrogance 
in science to regard practical men like us as blind men, and 
to attempt to make us see. How can men who know not 
whether potatoes should be planted in March or April, 
presume to teach us the properties which land suitable for 
potatoes ought to possess, — or what is the nature oi fallow? 
Such scientific explanations are not based on experience ; 
we can ourselves give much better. Whoever should 
attempt to depose farmyard manure from its exalted posi- 
tion deserves to be burnt alive ! 

Agriculturists had not yet acquired the faculty of dis- 
tinguishing between mere opinions and correct facts. 
Every fact was acceptable; every opinion was received 
by them. If science doubted the truth of one of their ex- 
planations^ they imagined that she ivas disputing their facts. 
If she asserted that a great progress would be made by 
substituting for stable manure its active constituents, they 
believed that in doing so she denied the efficacy of the 
former. 

About misunderstandings of this kind disputes then arose. 
The practical man did not yet understand the deductions 
of science. His dispute was with the bugbear of his own 
false conceptions, not with science. He did not know that 
science also has a moral of her own, the foundation of 
which lies in the precepts of the school and their practice 
in education. 

As a means of mental training, the study of the natural 
sciences was quite unknown to the practical man ; and 
hence the difficulty which existed between him and the 
scientific man of mutually understanding each other. Had 
the former turned his attention even in a slight degree to 
these sciences, he would of himself have acquired all the 



THEORETICAL AND PRACTICAL AGRICULTURE. 15 

information wliicli it now costs so mucli trouble to make 
intelligible to liim. 

In phj^sics and chemistry, disputes of tbis nature occur 
no longer, tbough the time is not long past since both 
were at that point of development which agriculture has 
still to pass. 

A glance at a chemical or physical journal must fill the 
mind of an agriculturist with astonishment at the mass of 
problems and their solutions which it contains, and at the 
immense labour which has been readily and without reward 
bestowed upon the whole. Each day brings its own pro- 
gress without strife, for each cultivator of these sciences 
knows what constitutes a fact, conclusion, rule, law, opinion, 
and explanation. There are specific tests for all these 
which every one uses, before he puts each to the test of 
its own peculiar touchstone, before he circulates the fruits 
of his labour. Each assiduously seeks to bring to light 
hidden facts, which are immediately submitted to proof by 
others, and receive their proper place when they are found 
to be genuine. One individual possesses the talent for seiz- 
ing the points of resemblance between two facts ; another 
has a keen eye for their differences ; in this way they render 
mutual assistance in the proper elucidation of phenomena. 
Special pleadings on the part of any one for his own pecu- 
liar views, without striking facts to support them, or the 
attempt to palm off on others any unproved facts, is in- 
stantly rebutted by the moral of science. The earnest desire 
of a mutual understanding is ever paramount. 

The most intelligent representatives of agriculture have 
hitherto erred in not discussing their questions in the way 
which would have led to the attainment of their object. 
Great agricultural associations, as well as individuals, have 
proposed questions, and recommended their solution as 
absolutely necessary for future progress. The majority of 



16 THEORETICAL AND PRACTICAL AGRICULTURE. 

agiiculturists liave a monomania for propounding such 
questions, and deceive themselves with the belief that their 
solution will be attended with sound practical information. 
Not one of them knows exactly what is wanted, but each is 
anxious to contribute his suggestions. Such questions pro- 
pounded by persons who know nothing of the subject are 
answered by others who understand it as little. Not one, 
however, really cares about the answer, for they all clearly 
see that they would not know what to do with it. 

There is a good method of satisfying ourselves of this 
fact. We have only in our minds to answer these ques- 
tions with "yes" or "no," or with any negative or positive 
number we choose, when the answer involves numbers, 
and we shall at once see that they are thoroughly unprac- 
tical, or belong to the same stamp as the prize question of a 
well-known Academy — "The decomposition of Nitrogen," 
a problem which now seems to us more difficult than the 
solution of charcoal for the purpose of making diamond. 
The solvers of such questions (and here I speak only of 
agriculturo-chemical), are hence always persons who do not 
possess the necessary knowledge to make the most trifling 
discovery. About fifteen years ago Hlubeck propounded 
a series of questions, on the solution of which the very 
existence of agriculture appeared to him to depend. Since 
then, neither he nor any other person has troubled himself 
about the matter ; and the j)resent state of the development 
of agriculture is a proof, that none of his questions stood 
in any relation to it, or exercised any influence upon its 
progress. 

These questions are always tokens of progress. They 
prove that agriculture has really passed from the state of 
blind empiricism into the first stage of its scientific develop- 
ment, viz. into that of its infancy, in which curiosity mani- 
fests itself by a multitude of questions. In this point of 



THEORETICAL AND PRACTICAL AGRICULTURE. 17 

view we may, after all, rejoice that such questions are 
really put. 

Chemistry and physics have likewise passed through the 
same stages. Academies and learned societies have in their 
time proposed an incredible number of absurd prize questions 
and impossible problems, without having thereby exercised 
any important influence on the furtherance of science. 
Those who are not well acquainted with the position in 
which these problems stand to science, would be easily 
misled into the belief that they have given origin to many 
truly substantial works. This is, however, an error, for the 
problems were proposed by those who knew that their solu- 
tion was already in progress ; or the questions came acciden- 
tally in the way of men who had been long previously 
occupied with them. 

Prizes, sometimes of a very high value, were attached by 
the Academies to the solution of their questions ; but as our 
excellent agriculturists regard the answering of their ques- 
tions as an honour, they may, on that account, calculate the 
more certainly that nobody will take any notice of them. 

At their great meetings the practical agriculturist com- 
municates his experience, and expresses his views. The 
final result is always a mutual agreement between those who 
differ in opinion ; and each goes home with the proud con- 
sciousness of having convinced the others that he is a man 
of progress, and has taken his part in it. Principles are 
left out of the question ; effective manures and experiments 
alone are wanted. Poor soils cannot be fertilised by funda- 
mental truths. 

A few years ago a writer expressed in such a meeting a 
modest doubt as to the duration of the nitrogen theory so 
strongly maintained in England, but they unanimously 
passed to the order of the day, as experience had long since 
decided the question of its value. 



18 THEORETICAL AND PRACTICAL AGRICULTURE. 

One of tlie worst points in the character of practical men, 
is their sensibility to opposition. The total want of founda- 
tion for their erroneous views is the reason why they regard 
them with so much affection and tenderness. It makes them 
blind to their own interest, and deaf to all instruction. 
They look on every one as an enemy who does not flatter 
their prejudices, who openly tells them that there yet remains 
much to be learned, and that the consciousness and confes- 
sion of our ignorance, and the knowledge of our faults, are 
the first steps towards improvement. I, who in my heart 
believe myself to be their most candid and sincere friend, 
must, therefore, at once make up my mind to bear with 
resignation the whole weight of their contempt, with which 
pride in their own experience fills them, if I attempt to 
prove the assertion, that the prevailing system of agriculture 
for half a century has been one of spoliation ; and that, if 
persisted in, the inevitable result will be, at no distant date, 
the ruin of their fields, and the impoverishment of their 
children and posterity. 



LETTEE II. 

Present prom is the leading principle of the prevailing system of Husbandry 
— This system is one of danger to Agriculture — Greneral view of the 
Nutrition of Plants — Atmospheric and Mineral Food — The absolute neces- 
sity to Plants of all the Constituents of their Mineral Food — Present 
views of the Nutrition of Plants erroneous — Rain water does not dissolve 
out the Mineral matters in the Soil — Remarkable absorbent power of Soils 
for the soluble Mineral Food of Plants, and particularly for Potash, Ammo- 
nia, and Phosphoric Acid— This power is limited, and varies with the Soil 
— Organic matter in the Soil materially modifies this power. 

Before proceeding to prove that our present system of 
agriculture is one of spoliation, I must from the outset 
remark, that I do not by this mean, that each agriculturist 
acts contrary to the rules of logic and common sense in 
tilling his ground in the manner most advantageous to him- 
self On the contrary, I feel satisfied that, so far as the 
attainment of this point is concerned, our practical agricul- 
turist is very reasonable and logical. He knows, in general, 
the means of rendering barren grounds fertile, and of obtain- 
ing the best crops from fertile fields ; and he employs these 
means with reflection and skill, for they have been known 
and proved for ages. 

A field from which a large crop of corn has been reaped, 
is again enabled to produce the same crop by mechanical 
preparation and by manure. Any peasant, who cannot 
read or write, knows that such a result will follow the 
employment of these two means. 

It is asserted, that the present system of husbandry 
yields greater crops, and produces more corn and meat, 



20 THEORETICAL AND PRACTICAL AGRICULTURE. 

with more profit, on the same area than formerly. I will 
not, at present, contest this point, and therefore it is not 
now my object to attack this system^ but rather to discuss 
the question, whether or not it is a rational one. If the 
large crops are a consequence of a mode of management 
by which the ground must gradually lose the conditions of 
its fertility, by which it must be impoverished and 
exhausted, then such a system is not rational^ though 
it enrich the individual who obtains these high returns. 

I am aware that the majority of agriculturists are fully 
satisfied that their mode of husbandry will insure a con- 
tinuance of fertihty to their fields. If I can succeed in 
awaking a doubt in this belief, I shall have gained an 
important point. The simple perception of their error will 
sufiice to lead to its correction. 

I hold it, indeed, to be no longer possible to bestow again 
upon the soil all those conditions of fertility which have 
been withdrawn by the existing mode of husbandry ; but, 
by a judicious system of management, so much may be 
accomplished with the still existing means, as to put in the 
shade all that has hitherto been done. 

To comprehend clearly the existing system of agricul- 
ture, we must recall to mind the most general conditions of 
the Ufe of plants. 

Plants contain combustible and incombustible constitu- 
ents. The latter, which compose the ash left by all parts 
of plants on combustion, consist in the case of our culti- 
vated plants, essentially of phosphoric acid^ potash^ silicic 
and sulphuric acids, lime, magnesia, iron, chloride of 
sodium. 

It is now regarded as an undisputed fact, that the consti- 
tuents of the ash are elements of food, and hence are 
indispensable to the structure of the different parts of the 
plant. Its combustible portion is derived from carbonic 



THEORETICAL AND PRACTICAL AGRICULTURE. 21 

acw^, water^ and ammonia, which as elements of food are 
equally indispensable. 

Bj the vital process plants are formed from these 
materials, when the atmosphere and soil supply them at 
the same time in suitable quantity, and in the proper pro- 
portions. The atmospheric elements do not nourish with- 
out the simultaneous action of the elements of the soil ; and 
the latter are equally valueless without the former. The 
presence of both is always required for the growth of the 
plant. 

It hence follows, as a matter of course, that no single 
element of the food of plants, named above, .possesses 
superiority over another : they are all of equal value to the 
life of the plant. But to the agriculturist, who must pro- 
vide a suitable supply of all these substances in his land to 
accomplish his particular object, they are, on the other 
hand, of unequal value. For should there be a deficiency 
of one of them, he can calculate on his crop only by sup- 
plying that particular one to the soil. The deficient or 
absent element then acquires a superior value, that is, in 
relation to the other matters (for example, lime in a lime 
soil), which the soil contains in greater quantity. 

All elements of food of plants belong to the mineral 
kingdom. The gaseous elements are taken up by the 
leaves ; the fixed by the roots. The first are frequently 
constituents of the soil, and, as such, reach the interior of 
plants by the roots as well as by the leaves. From their 
nature, these gaseous elements are movable; the incom- 
bustible ingredients are immovable, and cannot of them- 
selves leave the spot in which they are found. 

An element of food is ineffective if there be absent a 
single one of the other elements of food which are condi- 
tions of its activity. 

Corn plants, and those used for fodder, require for their 



22 THEOKETICAL AND PKACTICAL AGRICULTURE. 

development the same constituents, but in very unequal 
proportions. The successful growth of a green crop on a 
field, proves that it has found in the air and in the soil the 
atmospheric and mineral constituents of its food in the pro- 
portions suitable for its nourishment. The failure of a 
corn crop on the same field, indicates that in the soil there 
is something wanting which is necessary for its growth. 
Hence we must in every case of the failure of a cultivated 
crop, look to the ground for the cause, and not to any 
want of atmospheric food; for the same source of atmo- 
spheric food was available to the corn plant as to the green 
crop. 

But how does the soil act, and in what manner do its con- 
stituents take part in vegetation ? This question we shall 
now consider a little more in detail. 

The process of nutrition consists in the appropriation of 
food. A plant grows by increasing in bulk ; and its bulk 
increases by the constituents of its food becoming constituents 
of its frame. From carbonic acid, for example, sugar is 
formed ; silicic acid becomes a component part of the stem ; 
potash of the sap ; phosphoric acid, potash, lime, magnesia 
of the seed. 

In considering the effect of an element of food, we have 
to distinguish between the rapidity and the duration of its 
action. 

In general the result depends on the sum of the active 
elements available in the soil, in relation to the amount which 
the plant may altogether absorb, and does absorb, during 
the period of vegetation. A deficiency diminishes the crop, 
but an excess does not increase it beyond a certain limit. 
The excess comes into play in the succeeding period of 
vegetation. The continuous cultivation of crops is regulated 
by this excess which remains in the ground after each period 
of vegetation. If this residue is ten times greater than is 



THEORETICAL AND PRACTICAL AGRICULTURE. 23 

necessary for a full crop, then it will suffice for ten full crops 
during a period of ten years. 

The rapidity with which a substance, such as a piece of 
sugar, is dissolved by a fluid, is in proportion to its state of 
division. By pulverization its surface is increased, and con- 
sequently the number of points augmented, which, in a 
given time, are brought in contact with the dissolving fluid. 
In all chemical processes of this kind, the action proceeds 
from the surface. An element of food in a soil acts by its 
surface, the portion beneath the surface is inactive, because 
it cannot be dissolved. Its effect, within a given time, 
increases with the quantity taken up by the plant during 
that time. Fifty pounds of bones may in one year produce, 
according to their state of division, the same effect as one, 
two, or three hundred pounds coarsely ground. In the 
latter state it is by no means inefficient ; but to act, that is, 
to become soluble, it requires a longer time. The effect 
produced by it is smaller, but it continues longer. 

To understand correctly the effect of the soil and its con- 
stituents on vegetation, we must keep steadily in view the 
fact, that the elements of food present in it always possess 
within themselves active powers, but they are not always in 
a condition to exert this power. They are ready to enter into 
circulation, like a maiden to dance, but a partner is necessary. ^. 

The agriculturist requires eight substances in his soil, if j ^f '-♦^ 
all his plants are to flourish luxuriantly, or his fields to ! |\ -< 
produce the largest crops. Many of these, though not all, ^ 
are always present in quantity ; three require to be added 
to most fields. These eight substances are like eight links 
of a chain round a wheel. If one is weak, the chain is soon 
broken, and the missing link is always the most important, 
without which the machine cannot be put in motion by the 
wheel. The strength of the chain depends on the weakest 
of the links. 



24 THEORETICAL AND PRACTICAL AGRICULTURE. 

We have hitherto believed that plants received their food 
from a solution, and that the rapidity of its effect was in 
direct proportion to its solubility. We have supposed the 
active elements to be carried in solution in rain water and 
carbonic acid to their roots, and have regarded them in the 
light of sponges, half in the moist ground and half in the air, 
continuously absorbing by their roots the water which eva- 
porated from their leaves. Whatever was in solution passed 
with the water into the roots, and by the process of nutrition 
was appropriated by the plant. The soil and the plant were 
both passive in the operation. 

Vegetable physiology has taught, that an element of food 
in the soil, at a distance from the rootlets of plants, is avail- 
able as nourishment, provided there is water between the 
rootlets and the food to dissolve the latter. In consequence 
of the evaporation from the leaves, the rootlets suck up the 
water, which thus, with the substances dissolved in it, 
receives a movement onwards towards them. We believed 
that the water was the carrier of the most remote elements 
of the soil to the immediate presence of the plant. 

If 4000 lbs. of grain and 10,000 lbs. of straw require 100 
lbs. of potash and 50 lbs. of phosphoric acid for their deve- 
lopment, and if a hectare of ground contain these quantities 
in a soluble available form, then there will be sufficient for 
this crop. If the same field contain double, or a hundred 
times as much, then we should expect two or a hundred 
crops. This has been the physiological doctrine. 

But all this has been a great mistake. We have inferred 
from the effect of water and carbonic acid on rocks, a simi 
larity of action on soils ; hut this conclusion is false. 

There is not to be found in chemistry a more wonderful 
phenomenon, one which more confounds all human wisdom, 
than is presented by the soil of a garden or field. 

By the simplest experiment, any one may satisfy himself. 



THEORETICAL AND PRACTICAL AGRICULTURE. 25 

that rain water filtered tlirougli field or garden soil, does not 
dissolve out a trace of potash^ silicic acid^ ammonia^ or phos- 
phoric acid. The soil does not give up to the water one 
particle of the food of plants which it contains. The 
most continuous rain cannot remove from the field, except 
mechanicallj, any of the essential constituents of its fertility. 

The soil not only retains firmly all the food of plants 
which is actually in it, but its power to preserve all that may 
be useful to them, extends much further. If rain or other 
water, holding in solution ammonia^ potash^ phosphoric and 
silicic acids^ be brought in contact with the soil, these sub- 
stances disappear almost immediately from the solution ; the 
soil withdraws them from the water. Only such substances 
are completely withdrawn by the soil as are indispensable 
articles of food for plants ; all others remain wholly or in 
part in solution. 

If a funnel be filled with soil, and a dilute solution of 
silicate of potash be poured upon it, there will not be found 
in the filtered water a trace of potash^ and only under cer- 
tain circumstances silicic acid. 

If freshly precipitated phosphate of lime, or phosphate of 
magnesia, be dissolved in water saturated with carbonic acid, 
and filtered in like manner through soil, there will not be 
found a trace of phosphoric acid in the filtered water. A 
solution of phosphate of lime in dilute sulphuric acid, or of 
phosphate of magnesia and ammonia in carbonic acid water, 
comports itself in the same manner. The phosphoric acid 
of the phosphate of lime, and the phosphoric acid and 
ammonia of the magnesia salt remain in the soil. 

Charcoal re-acts in a similar manner with many soluble 
salts ; it removes colouring matter and salts from solutions. 
It is natural to look upon the effect in both cases as pro- 
ceeding from the same cause. In the case of charcoal, it is 
a chemical attraction, which proceeds from its surface; 



26 THEOKETICAL AND PKACTICAL AGRICULTURE. 

but the constituents of the soil take part in its action, and 
hence it must in many cases be quite different from that 
of charcoal. 

Potash and soda are well known to stand to each other 
in the closest chemical relation, and even their salts have 
many properties in common. Chloride of potassium, for 
example, has the same crystalline form as chloride of 
sodium ; and in taste and solubility they differ but slightly. 
An unpractised eye can scarcely distinguish them, but the 
soil can do this in the most perfect manner. 

If we add any soil in powder to a dilute solution of 
chloride of potassium, in a short time there will not be 
found any potassium in solution. The same quantity of 
earth does not withdraw from a solution of chloride of 
sodium, containing ah equal amount of chlorine, even the 
half of the sodium. Consequently, a complete decomposition 
takes place with the potassium, but only in part with the 
sodium. Potash is found in all our land plants, but soda 
forms only an exceptional constituent of their ashes. From 
sulphate and nitrate of soda, the soil withdraws only a part 
of the soda, but the whole of the potash from the corres- 
ponding potash salts. Experiments, expressly made for this 
purpose, have shown that 1 litre = 1000 cubic centimetres 
(=61 cubic inches Eng.) of garden soil, rich in lime, will 
take up the potash from 2025 cub. cent. (= 123'6 cub. 
inches, or 8i pints) of a solution of silicate of potash, which 
contains in every 1000 cub. cent. 2-78 grammes (:= 43 grs.) 
of silicic acid, and 1166 grammes {= 18 grs.) of potash. 
From these data we can calculate that a field of a hectare 
{= 2i acres) in extent, and having a depth of i of a metre 
— 10 inches nearly) of soil, of the sanje kind as that used 
in the experiments, would withdraw from a similar solution 
more than 100,000 lbs. of potash, and retain them for the 
use of plants. A similar experiment, made with a solu- 



THEORETICAL AND PRACTICAL AGRICULTURE. 27 

tion of phosphate of magnesia and ammonia in carbonic acid 
water, showed that a 2^ acre field would withdraw 5000 
lbs. of this salt from such a solution. A loam (poor in 
lime) produces the same effect. 

These facts give us some conception of the powerful 
action of soils, and of the strength of their attraction for 
three of the chief elements of the food of our cultivated 
plants, which, in consequence of their solubility in pure and 
carbonic acid water, could not be retained in the soil, did 
the latter not possess this power of attraction.* 

From stale urine^ liquid manure diluted with much water, 
or from a solution of guano, soil, when used in sufficient 
quantity, removes the whole of the ammonia^ potash^ and 
phosphoric acid which they contain. Not a trace of these 
substances can be found in the water which flows from the 
soil. (Thompson, Huxtable, Way.)t 

* These experiments are so simple and so easily performed, that they may 
be exhibited at lectures. In filtering, care must be taken that the fluid does 
not form canals, which would prevent the complete contact of the solutions 
with the soil. Yery dilute solutions of silicate of potash, chloride of potas- 
sium, &c., must therefore be used, in the proportion, for example, of one part 
of substance to 500 of water. Saturated solutions of the other substances, such 
as phosphate of lime in carbonic acid, may be employed. Generally, in the 
first portions of filtrate from the phosphate of lime, not a trace of phosphoric 
acid can be detected by molybdate of ammonia. A solution of silicate of 
potash, which re-acts distinctly alkaline with turmeric paper, instantly loses 
this re-action by simple mixture with soil. This power of absorption in soils 
for ammonia was observed by Thompson, and for phosphoric acid and some 
potash salts by "Way, so long ago as 1850 ; but up to that time neither 
vegetable physiologists, nor scientific agriculturists, had taken notice of the 
remarkable discoveries of these English chemists, so pregnant with important 
results to physiology and agriculture. 

\ I cannot here omit a circumstance communicated to me a few years ago 
by Dr. Marquart, of Bonn, and which illustrates, in a remarkable enough 
manner, the power of absorption of clays for ammonia. 

A manufacturer on the Rhine conceived the idea of extracting, by means 
of ammonia, the oxide of copper, which was found as malachite and azure- 



28 THEORETICAL AND PRACTICAL AGRICULTURE. 

The power possessed by soils to withdraw ammonia, pot- 
ash, phosphoric and silicic acid, from solution, is limited. 
Each soil is endowed with its own peculiar capacity in this 
respect. When brought in contact with these different 
solutions, the soil becomes saturated with the dissolved 
matter, and the excess of soluble substance then remains 
in solution, and can be detected by the ordinary re-agents. 
A sandy soil absorbs less than the same volume of a marly 
soil. And the latter less than a clay soil. The variations 
in the quantity of matter absorbed are as great as the differ- 
ences existing among the soils. We know that no two are 
alike ; and it is not improbable that certain peculiarities in 
cultivation stand in a certain relation to the unequal power 
of the different soils for absorbing one of the above sub- 
stances. It is not impossible, that, by a closer study of 
this relation, we may arrive at quite new and unexpected 

spar dispersed through shale. The experiment had succeeded with him on a 
small scale. At a considerable expense he constructed a large extraction 
apparatus, consisting of two boilers connected by a very wide tube. The 
fluid ammonia was placed in one boiler ; the tube was filled with the shale ; 
and the second boiler served as condenser. By this arrangement it was 
intended that the ammonia and vapour of water should be condensed in the 
tube, and, after dissolving the oxide of copper, pass over into the second 
boiler. The tube was then to be filled with fresh shale, the ammonia to be 
driven by heat from the solution in the second boiler, and made again to 
extract the copper from the fresh shale. As the whole apparatus was her- 
metically closed, it was hoped that the same quantity of ammonia would serve 
without loss to extract large quantities of shale. The boilers were employed 
alternately as condensers. The first trial was so far successful, that a solution 
of oxide of copper really collected in one of the boilers. But on passing the 
ammonia through a second portion of shale, it disappeared in a manner most 
incomprehensible to the manufacturer. The process had in consequence to 
be abandoned. The disappearance of the ammonia in this operation was 
undoubtedly due to the absorbent power of the clay of the shale. This fact 
may be taken as a proof of the powerful attraction existing between these 
two substances, which apparently could not be overcome even by the influ- 
ence of a high temperature. 



THEORETICAL AND PRACTICAL AGRICULTURE. 29 

means of judging of the agricultural value or fertility of 
our fields. 

The action of a soil, rich in organic matter, on the solu- 
tions above mentioned, is worthy of remark. A clay or 
lime soil, poor in organic matter, withdraws all the potash 
and silicic acid from a solution of silicate of potash ; 
whereas one rich in so-called humus extracts the potash, but 
leaves the silicic acid in solution. This comportment invo- 
luntarily recalls the action of decaying vegetable remains in 
the soil on the growth of plants, which, like reeds and 
horse-tails, require a large quantity of silicic acid. These 
plants abound in so-called sour moor and meadow lands ; 
but disappear from them on the application of lime, and 
give place to others better fitted for fodder. 

Experiment shows, that the same garden and forest soil, 
rich in humus, which withdraws no silicic acid from a solu- 
tion of silicate of potash, immediately acquires the power 
to do so, if it be mixed with a little slaked lime before the 
silicate is added to it. Both constituents, potash and silicic 
acid, are then retained by the soil. 



LETTER ni. 

Our cultivated plants do not receive their food from Solution — Roots of plants 
derive their Nourishment only from those portions of Soil absolutely in 
contact with them — This view supported by the composition of River, 
Well, and Drainage water — The Roots of plants must themselves exert 
some peculiar action in Nutrition — The Life of land-plants endangered by 
food when in Solution — In Water-plants the laws for the absorption of 
Food must differ from those of Land-plants — The Ash of duck- weed shows 
that plants have a Power of selecting their Food — Reason why mud from 
stagnant pools is a good Manure — Remarkable power for absorbing Mois- 
ture possessed by Soils — By absorption and evaporation of Moisture, the 
Soil is warmed or cooled — G-reat importance of this fact to Vegetation — 
The two Sources from which Moisture is absorbed by the Soil — Natural 
Law deduced from the above facts. 

There can be no doubt, from the action just described 
of soil on potash, ammonia, and phosphoric acid, that the 
majority of our cultivated plants cannot receive out of a 
solution from the soil their essential mineral constituents. 
For if, after filtering a solution of potash or ammonia 
through a layer of soil of no greater thickness than usually 
occurs in a field, these substances are so completely with- 
drawn from the powerful acids with which they are com- 
bined, as well as from the watery solution, that chemical 
analysis can scarcely detect a trace of them in the filtrate, 
it is not probable that rain-water alone, or even by the aid 
of a small per-centage of carbonic acid, should possess the 
power of extracting them from the soil, and forming a solu- 
tion which should not again be decomposed by passing 
through the ground. The same fact holds good for phos- 
phoric acid and its salts. Carbonic acid water will every- 



THEORETICAL AND PRACTICAL AGRICULTURE. 31 

where dissolve phosphate of lime when it comes in contact 
with it ; and the consequence of this solution can only be 
its distribution through the soil. But such a solution 
could not pass from the spot in which it was formed with- 
out being deprived of all the dissolved salt bj such por- 
tions of the soil as are not already saturated with it. 

These substances are present in the soil in a condition 
somewhat like colouring matter in charcoal, or iodine in 
starch, fit for absorption by the rootlets of plants, but 
not by themselves soluble in rain water, or removable by 
this solvent until the soil is saturated with them. 

It is more than probable that it is assigned to the 
majority of our cultivated plants to receive their nourish- 
ment directly from those portions of soil which are in 
immediate contact with their rootlets, and that they die 
when their food is presented to them in solution. The 
action of concentrated manures, which are said by agricul- 
turists to hum the young plants, appears to stand in some 
connection with this supposition. 

The composition of our common river, well, and drain- 
age water from land, may serve to support these conclusions. 

A number of excellent analyses of river and well 
waters has been published by Graham, Miller, and Hof- 
mann (Chem. Soc. Qu. T. iv. 375), from which it appears 
that 100,000 gallons, or 500 tons of Thames water, taken 
from five different places, contain : — 

Thames Ditton, Kew. Barnes. Kedhouse, Battersea. Lambeth, 
Pounds of Potash, 7-3 4-71 3-55 10 7-3 

The following well waters contain, in 100,000 gallons : — 

Witley. Critchmere. Veil wool. Hindhead. Barford. Cosford House. 
Pounds of Potash, 2-71 25 3 0-7 1-8 6 

Thomas Way found in drainage water — that is, in rain- 
water (which had naturally percolated through the soil), 



82 



THEORETICAL AND PRACTICAL AGRICULTURE. 



taken from seven different fields, the following constituents 
(Journal of the Roy. Ag. Soc, vol. xvii. 133) : 



' 


Grains in 1 Gallon — 70,000 grains of water. 


1 


2 


3 


4 


5 


6 


7 


Potash 


Trace 
1-00 
4-85 
0-68 
0-40 
0-95 
070 
1-65 

Trace 
0018 


Trace 
2-17 
7-19 
2-32 
0-05 
0-45 
1-10 
5-15 
012 
0018 


0-02 
2-26 
6-05 
2-48 
010 
0-55 
1-27 
4-40 
Trace 
0018 


0-05 
0-87 
2-26 
0-41 

1-20 
0-81 
1-71 
Trace 
0-012 


Trace 
1-42 
2-52 
0-21 
1-30 
1-80 
1-26 
1-29 
0-08 
0-018 


0-22 
1-40 
5-82 
0-93 
0-35 
0-65 
1-21 
3-12 
0-06 
0-018 


Trace 
3-20 

13-00 
2 50 
0-50 
085 
262 
951 
012 
0-006 


Soda 


Lime 


Magnesia 


Iron and Alumina. . 
Silica 


Chlorine 


Sulphuric acid 

Phosphoric acid 

Ammonia 





Very similar results were obtained by Dr. Krocker from 
his analysis of drainage water from Proskau (Lieb. and 
Kopp's Jahr., £ 1853, p. 742) : - 





Drainage Water (in 10,000 parts). 


a 


b 


c 


d 


e 


f* 


Organic matter 


0-25 
0-84 
2-08 
02 
0-70 
004 
002 
0-11 
0-08 
0-07 


0-24 
0-84 
210 
002 
0-69 
004 
0-02 
015 
008 
0-07 


0-16 
127 
1-14 
0-01 
0-47 
0-04 
02 
013 
007 
006 


06 
0-79 
017 
002 
0-27 
0-02 
002 
010 
03 
0-05 


0-63 
0-71 
077 
0-02 
0-27 
0-02 
04 
005 
001 
006 


0-56 
0-84 
0-72 
0-»2 
0-16 
001 
0-06 
0-04 
0-01 
0-05 


Carbonate of lime 


Sulphate of lime. .' 


Nitrate of lime 


Carbonate of magnesia 

Carbonate of iron 


Potash 


Soda 


Chloride of sodium 

Silica 




Total solid matter 


4-21 


4-25 


3-37 


1-53 


2-58 


2-47 



* a Drainage water from land A (a clay soil resting on a subsoil of chalky 
loam), collected 1st of April, 1853. b The same, collected 1st of May, 1853, 



THEOKETICAL AND PKACTICAL AGRICULTURE. 33 

These drainage waters contain all the substances which 
rain-water can dissolve out of the soil, and from their com- 
position an idea may be formed of the quantity which a 
plant during the period of its growth can possibly obtain 
from such a solution. 

Let us assume that on a 2^ acre field 12 million pounds 
of rain-water fall in a year, and that a third of this quantity 
dissolves from the soil the same ingredients, in the same 
proportions, as in the drainage waters analysed by Way. 
Let us further suppose that these 4 million pounds of water 
are, during the months of June, July, August, and Septem- 
ber, completely absorbed by the roots of a crop of potatoes, 
and again evaporated from the leaves ; then it follows that 
on four fields of 2^ acres each, the whole crop of potatoes 
would not receive a single pound of potash ; on two others 
of the same size they would obtain rather more than a 
pound ; and on a seventh 2| acre field, two pounds. 

Now, from an average crop of potatoes on a 2^ acre 
field, there are obtained 408 lbs. of ashes, in which are 
contained 200 lbs. of potash. 

If, again, we suppose a crop of beet to be grown on the 
fields, of which Dr. Krocker analysed the drainage water, 
and also assume that 4 million pounds of rain-water satu- 
rated with mineral substances from the soil, are absorbed 
by the crop, then these plants would receive from this 
source on four difierent fields of 2^ acres each, only 8 lbs. 
each ; on another, 16 lbs. ; and on a third, 24 lbs. of 
potash. 

after a heavy fall of rain (218 cub. in. on the square foot), c Drainage water 
from the same soil, mixed with water from a humus clay soil, with chalky 
loam as subsoil, collected in October, 1853. d Drainage water from land B 
(tile-drained, subsoil of chalky loam) collected in October, 1853. e Water 
passing through the water furrows from a heavy clay soil, collected in the 
beginning of June, f The same, collected in the middle of August, after 
heavy rain. 

2* 



84 THEORETICAL AND PRACTICAL AGRICULTURE. 

Now, an average crop of beet from 2|- acres weiglis, witli 
leaves, about 1000 cwt., whicli contain 1,144 lbs. of ashes, 
of which 495 lbs. are potash I 

The quantity of ammonia present in the drainage waters 
analysed by Way is exceedingly small. It is not very 
probable that one pound of ammonia in 8^- million pounds 
of water can exercise any marked influence on vegetation. 

In a gallon (70,000 grs.) of Thames water taken from 
four different places, the quantity of ammonia could not be 
estimated. In the portion taken at Eed-house, Battersea, 
there were found 3 of ammonia, in 7 million parts of 
water (Lieb. and Kopp's Jahr., f. 1851, p. 658). By irri- 
gation the Thames water would undoubtedly produce a 
considerable increase in the crops of hay on many mea- 
dows, but certainly not by its ammonia, which is present in 
this, as well as in all river waters in general, in only very 
minute quantities. 

The amount of phosphoric acid in drain, river, and ordi- 
nary well-water, is exactly nil. Krocker found in drainage 
water no phosphoric acid ; Way obtained from three, only 
traces ; in two others, he found 12 parts of phosphoric acid 
in 7 million parts of water ; in a third, 8 parts, and in a 
fourth, 6 parts of phosphoric acid, to the same quantity of 
water. 

From the action of soils already described, it follows 
that plants must themselves play some peculiar part in the 
absorption of their food. As organised living structures, 
their existence is not quite dependent on external causes. 

Did land plants receive their food from a solution, they 
should only be able to take up what this solution contains 
and brings to them in a certain time, and just in proportion 
to the evaporation of the water from their leaves. It is 
quite certain that in the process of assimilation, there is a 
necessary co-operation between the water which soaks 



THEORETICAL AND PRACTICAL AGRICULTURE. 35 

through the ground, and the evaporation which takes place 
from the leaves of plants ; but the ground itself plays the 
part of a guardian, protecting plants from a hurtful supply. 
They select from the soil those substances which they re- 
quire, but which can only pass into the interior of their 
organisms by the co-operation of a cause which resides 
within the rootlets. 

We frequently find in meadows smooth lime-stones, 
with their surfaces covered with a network of small fur- 
rows. When these stones are newly taken out of the 
ground, we find that each furrow corresponds to a rootlet, 
which appears as if it had eaten into the stone. 

It is very difficult to explain in what way plants act in 
causing the solution of mineral substances. As a matter of 
course, water is indispensable in the operation. 

The difficulty of explaining the facts ought not at once 
to deter us from investigating them in all their bearings, 
and ascertaining the extent of their influence. Exceptions 
exist in abundance. 

In the case of many water plants whose roots do not 
come in contact with the ground, there must of course 
exist other laws for the absorption of their mineral food. 
As in the case of sea-plants, they must receive it from 
the surrounding medium ; for, wherever a plant grows, it 
must find all the conditions necessary to its existence. 

The investigation of duckweed (Lemna trisulca) offers in 
this respect some points of interest. This plant grows in 
still waters, in ponds and bogs, floating on the surface, so 
that its roots are not in contact with the bottom. 

From an artificial piece of bog in the botanic garden of 
this place (Munich), a quantity of this plant was collected, 
dried, incinerated, and the amount of ash determined. 
From 10 to 15 litres (21- to 3^ galls.), of the bog water 
which was of a slight greenish tint, was at the same time 



36 



THEOKETICAL AND PRACTICAL AGRICULTURE. 



filtered and evaporated to dryness. The ashes, as well as 
the residue from evaporation of the water, were submitted 
to analysis. For comparison, the results are here placed 
together. 



Ash of Duckweed. 



100 parts of dried duckweed, give 


16-6 parts of Ash. In 100 


parts of 


the Ash heated to low redness, are 


contained: — 




Lime ... 


16-82 


Magnesia .... 


5 08 


Chloride of sodium . . . 


5-897 


Chloride of potassium . 


1-45 


Potash 


13-16 


Soda 




Oxide of iron with traces of 




alumina 


. 1-3Q 


Phosphoric acid . . . 


. S-YS 


Sulphuric acid . 


. 6-09 


Silica .... 


12-35 



Evaporated residue from water of the 
Botanic Gardens. 

1 Litre gives 0-415 grm. salts 
(heated to low redness). In 100 
parts of the salts are contained : — 

35-00 

12.264 

10-10 



8-97 
0-471 

0721 
2-619 
8-271 
3-24 



The amount of mineral constituents of this plant, as well 
as of the bog water, must strike others with the same as- 
tonishment as it did the first observer. For we could not 
presuppose that such a plant should far surpass the ma- 
jority of land plants in the richness of its mineral con- 
stituents. These were certainly taken up by the plant from 
a solution ; but in the process, it is highly deserving of 
remark, that a power of selection was exercised by the 
plant. 

The comparison of the composition of the ash with the 
salts left by the water shows, that all the mineral constitu- 
ents of the latter, with the exception of the soda, are found 
in the plant, but in very altered proportions ; the water 
contains 45 per cent, of lime and magnesia, the plant only 
21 per cent, of both ; the water contains 0*72 per cent, of 



THEORETICAL AND PRACTICAL AGRICULTURE. 87 

oxide of iron, tlie plant ten times this quantity. The dif- 
ference in the phosphoric acid, potash, &c., is not less strik- 
ing. The soluble mineral constituents were taken up by 
the plant in the various degrees required for its vital pro- 
cesses, and in no way proportional to the amount present 
in the fluid. 

The amount of mineral water present in this water is 
remarkable. It is more than ten times greater than in 
drainage water, and twenty -five to thirty times greater than 
in well water. It resembles a mineral water in the kind 
of salts it contains, and except in bogs is not likely to occur 
in nature. 

The amount of potash, phosphoric, sulphuric, and silicic 
acids, and oxide of iron, which is found in it, can be easily 
explained. In such a bog, the remains of dead plants are 
by degrees collected, the roots of which have received from 
the soil a quantity of mineral matter. These remains un- 
dergo decomposition at the bottom of the pool, and their 
inorganic elements are dissolved by the aid of carbonic 
acid, and probably of organic acids, and remain in solution 
in the water after the surrounding mud and earth have 
been completely saturated with them. An experiment, in 
fact, showed, that this potash water lost none of its potash 
on filtration through earth taken at the distance of a foot 
from the edge of the basin, whilst it was quickly removed 
by earth taken from other spots. 

In many places the mud from pools, still waters, and 
many bogs, is highly esteemed as a fertilising agent. It is 
evident that such mud acts like arable soil which has ab- 
sorbed as much as it is capable of doing of the soluble 
elements of food or manure brought in contact with it, 
and a satisfactory explanation of its effect is found in the 
quality of the bog water. Finally, it is conceivable that 
water, in percolating through many field and garden soils, 



88 THEOEETICAL AND PRACTICAL AGRICULTURE. 

in which the remains of plants have accumulated, and are 
undergoing decomposition, will dissolve up many sub- 
stances not usually found in mineral waters. 

With the chemical properties of soils just described, there 
is associated a physical quality, not less remarkable in its 
nature and influence ; viz., the power which they possess 
of attracting moisture from the air, and condensing it in 
their pores. It has been long known that earth possesses a 
strong attraction for watery vapour, but it was to Babo 
that we were first indebted for the proof that this attrac- 
tion is only second to that of sulphuric acid, which pos- 
sesses it in the highest degree. If we fill a flask with air 
completely saturated with moisture at 20*^ C. (68° Fahr.), 
the slightest diminution of temperature will cause the 
moisture to be deposited in the form of dew ; but if a 
few ounces of earth dried at 85° to 40^ C. (95° to 204° 
Fahr.), be placed in the flask, the moisture will, in the 
course of a few minutes, be so completely absorbed by it, 
that no deposit of dew will take place at a temperature 
even of 8° to 10° C. below 0° (14° to 18° Fahr.). The ten- 
sion of the watery vapour has sunk from 17"^^ to less than 

Oram 

In very moist air, soil loses its absorbing power for 
moisture in proportion as it becomes saturated. When per- 
fectly saturated it no longer absorbs any moisture from the 
air. From air of the temperature of 20° C. (68° Fahr.), 
containing watery vapour with a tension of more than 2""™, 
dry earth absorbs moisture, until an equilibrium is esta- 
blished between the tension of the watery vapour in the 
air, or the force which strives to maintain it in the gaseous 
state, and the power of attraction in the earth which tends 
to destroy this state. 

A soil which has been saturated with moisture from the 
air at a given temperature, gives off a certain portion to 



THEORETICAL AND PRACTICAL AGRICULTURE. 89 

drier air, or on an elevation of temperature. On the other 
hand, it absorbs moisture from air still more moist, until 
an equilibrium is established. 

The processes of absorption and evaporation are accom- 
panied by a most important phenomenon. By absorption 
of moisture the soil is warmed, and by evaporation it is 1 
cooled. If we suspend in a vessel with moist air, a linen 
bag full of dry earth, with a thermometer sunk in it, the 
quicksilver will be observed to rise in a few seconds. In 
Babo's experiment the temperature rose, in a specimen of 
soil rich in organic matter, from 20° to 81° C. (68° to 88° 
Fahr.) ; in a sandy soil to 27° C. (80° Fahr.). In like man- 
ner, soil which had been partly saturated with moisture 
from air at 68° Fahr. and 54° dew-point, when placed in 
air completely saturated with moisture, caused the tempera- 
ture to rise 8*6° to 54° Fahr. Such phenomena as these 
must exercise a most decided influence on vegetation ; for 
though the above extremes in the elevation of temperature 
are seldom observed, the intermediate points are of frequent 
occurrence. 

When in a hot summer the surface of the ground is dried, 
and there is no replacement of moisture by capillary attrac- 
tion from the deeper strata, the powerful attraction of the 
soil for the vapours of water in the air provides the means 
for supporting vegetation. 

The vapour of water which is thus condensed by the soil 
is derived from two sources. During the night the tempe- 
rature of the air falls ; the tension of its watery vapour be- 
comes less ; and then, without the temperature of the air 
falling to the dew-point, there follows, through the attrac- 
tion of the soil, absorption of moisture (with ammonia and 
carbonic acid), accompanied by evolution of heat which 
moderates the cooling of the ground from radiation. In 
rainless tropical regions, particularly, this phenomenon 



40 THEOEETICAL AND PRACTICAL AGRICULTURE. 

must be of the most palpable influence. If in our tempe- 
rate climate its effect is not so striking as in these regions, it 
is nevertheless not to be regarded as altogether inappreci- 
able. As condensation takes place slowly, the elevation 
of temperature here cannot amount in many cases to more 
than fractions of a degree. But it is precisely those frac- 
tions which promote the better growth of many plants. 
The soil by means of this property of absorption becomes 
warmer, and maintains its temperature more equably than 
it would otherwise do. 

A second source from which the dry soil derives by 
absorption its moisture, is presented by the deeper lying 
moist strata. From these a constant distillation of water is 
taking place towards the surface, accompanied by a corre- 
sponding evolution of heat in the upper strata on its absorp- 
tion. By drainage the water, which rises by capillary 
attraction, being placed at a greater depth, the dry soil now 
receives from the lower strata a quantity of moisture in the 
form of vapour, which supplies the wants of plants, and at 
the same time raises the temperature of the ground. 

In the above facts we recognise one of the most remark- 
able natural laws. The outermost crust of the earth is destined 
for the development of organic life^ and its broken particles are 
endowed^ by the wisest arrangement^ ivith the power of collecting 
and retaining all the elements of food lohich are essential for the 
purpose. This power preserves to the productive soil, even 
in apparently the most unfavourable circumstances, the con- 
ditions of fertility either contained therein, or bestowed 
upon it. 



LETTER IV. 

The Belief in the value of Humus no longer exists ; its Action now ascertained 
— Effect of the Salts of Ammonia not dependent on their Nitrogen — The 
action of Nitrates like that of the Salts of Ammonia — Experiments with 
Nitrates and Chlorides — Experiments with Salts of Ammonia alone, and 
with the addition of Common Salt — Solubility of the Earthy Phosphates in 
solutions of Chlorides of Ammonium and of Sodium, and of Nitrate of Soda 
— Experiments with these Salts — Their Solvent Action similar to that of 
Carbonic Acid water — The Salts of Ammonia are decomposed in the soil ; 
their twofold action — Difference in the Comportment of Salts of Potash and 
of Soda in the Soil — Potash extracted by Sulphate of Ammonia from silicates 
— Application of the Action of Chili Saltpetre, Salts of Ammonia, and 
Chloride of Sodium to explain the increase of fertility in the soil, and the 
Nutrition of Plants. 

Up to a few years ago, scientific agriculture taught, and all 
practical men firmly believed, that the productiveness of a 
soil was dependent on the quantity of humus, or carbonaceous 
remains of a preceding vegetation, contained in it. Without 
raising doubts on the efiicacy in certain cases of the organic 
matter in farm-yard manure, it may be asserted that nobody 
who possesses any knowledge of the matter, now believes 
that the produce of a field in carbonaceous substances bears 
any proportion to the amount of humus in the soil, and that 
its fertility can in reality be estimated, as was formerly sup- 
posed, by this humus. 

We have now obtained more exact information on the 
part played by humus in vegetation, and can predict in what 
cases its presence will be beneficial or hurtful. We know 
that it is only useful when the soil contains in sufficient 
quantity the fixed mineral constituents serviceable to plants ; 



42 THEORETICAL AND PRACTICAL AGRICULTURE. 

and that it is without action when these are wanting By 
its decomposition in the soil, humus forms a source of car- 
bonic acid, by which the fixed elements of food are rendered 
soluble, and capable of being distributed in all directions. 

In his remarkable experiments on the action of the salts 
of ammonia, Lawes obtained in twelve years from an acre 
of the same field, by the use of mineral substances and salts 
of ammonia, produce in wheat and straw, amounting to 
51,995 lbs. From a second acre manured in the same way, 
the return reached 53,182 lbs. By the use of pure mineral 
manures, there was obtained from these two fields a greater 
amount of produce, to the extent of 18,525 lbs. in one case, 
and 19,713 in the other, than from an unmanured field of 
similar size. It is quite certain that by the employment of 
farm-yard manure, a similar, if not higher, return would 
have been obtained from both fields. There can, however, 
be no doubt that in both cases the salts of ammonia had 
taken the place, and produced the effect of the decaying 
organic matter of this manure; and it is not improbable 
that the same cause was in operation in augmenting the 
produ(3e. 

It has been abundantly proved by facts, that the action 
of the salts of ammonia is no way proportional to the amount 
of nitrogen in them ; hence it is evident that the salts as 
such, or the acids of the salts, must take part in the efiect 
produced. The precise nature of this co-operation is, how- 
ever, not yet distinctly made out ; and from this cause has 
arisen the great discordance in the views of the peculiar 
action of the salts of ammonia. Whilst some hold that the 
action can only be referred to the nitrogen, because the acid 
can be changed without thereby materially altering the 
effect ; others assert that the soil already contains so much 
ammonia, that the increase of produce cannot be attributed 
to the small quantity of nitrogen added in the salts of 



THEORETICAL AND PRACTICAL AGRICULTURE. 43 

ammonia. They maintain tliat an acre of ground which 
contains in its upper ten inches of soil 10,000 lbs. of 
ammonia or nitrogen, could not have its fertility increased 
two-fold by the addition of 30 to 60 lbs. of ammonia. As 
in such a soil there was no want of nitrogen, the cause of 
the increased fertility must be sought for in something 
else. 

The case is much the same with the action of nitrates as 
with that of the salts of ammonia. Nitrate of soda exer- 
cises a powerful effect, in certain cases, on the increase of 
grain and straw, and in others it is valueless. The experi- 
ments of Kuhlmann have shown that the bases also of these 
salts play some part in the action. From a meadow ma- 
nured with 250 kilogrammes (550 lbs.) of nitrate of soda, 
an increase of crop to the amount of 2053 kilo. (4516 lbs.), 
per hectare (2-J- acres), was obtained ; whilst from another 
portion of the same meadow, to which was applied the 
same quantity of nitrate of lime (containing IJ per cent, 
more nitric acid), there was an increase of only 693 kilo. 
(1524 lbs.). Consequently the produce from nitrate of lime 
was f less than from the soda salt. If we ascribe the 
increase in the crop to the nitric acid, then the effect of 
the two salts is quite incomprehensible. 

The action of common salt appears in many cases equally 
incomprehensible. In 1846, Kuhlmann obtained from 200 
kilo. (440 lbs.) of sulphate of ammonia an increase of hay, 
amounting to 2533 kilo. (5572 lbs.) ; a similar quantity of 
sulphate of ammonia, with the addition of 133 kilo. (292 
lbs.) of common salt, gave an increase of 3173 kilo. (6980 
lbs.) of hay. There were consequently 640 kilo. (1408 lbs.) 
more hay obtained by the addition of the common salt, 
than from the employment of the sulphate of ammonia 
alone. 

It might be supposed, that the want of a chlorine com- 



44 THEORETICAL AND PRACTICAL AGRICULTUEE. 

pound, whicli is contained in not inconsiderable quantity in 
meadow plants, was the reason, in the case of the common 
salt, of the increase of produce ; but a similar difference, as 
in the above cases, was found in two other experiments, 
which Kuhlmann made, in 1845 and 1846, with sal-ammo- 
niac alone, and with sal-ammoniac and common salt. The 
piece of meadow manured with 200 kilo. (440 lbs.) of sal- 
ammoniac gave in the two years 3700 kilo. (8140 lbs.) per 
hectare (2-J acres), more hay than a piece of the same extent 
which was unman ured. From another portion, to which 
were applied 200 kilo, of sal-ammoniac and 200 kilo, of 
common salt, 5687 kilo. (12,511 lbs.) of hay were obtained. 
Hence, by the use of common salt, there was an increase 
of 1087 kilo. (2391 lbs.), or a half more than from the sal- 
ammoniac alone. 200 kilo, of common salt alone, without 
sal-ammoniac, produced an increase of 1606 kilo, of hay, 
the difference between the two numbers (1987 and 1606 
kilo.) is not great enough to exclude the idea, that each 
salt has acted, just as if the other had not been present, or, 
in other words, that each salt has a special action of its 
own. 

In the summer of 1857, the effect of salts of ammonia by 
themselves, and mixed with common salt, on summer bar- 
ley, was tried by the General Committee of the Agricul- 
tural Society of Bavaria, in a series of experiments made 
at Bogenhausen, in the neighbourhood of Munich. For 
this purpose, 18 plots, each of 1914 square feet in extent, 
were marked off in a field which had gone through the 
usual rotation of crops, having been, three years previously, 
manured with common farm-yard manure, and having 
borne rye, and then two crops of oats. Four of these plots 
were manured with salts of ammonia ; one remained unma- 
nured ; to four others were applied the same quantity of 
ammonia salts, and at the same time, to each 3080 grm. 



THEORETICAL AND PRACTICAL AGRICULTURE. 45 

(6^ lbs.) of common salt. Each plot received tlie same 
amount ofniirogcn in the ammonia salts. 

In estimating the quantity of manuring matter to be 
employed, it was assumed that 400 lbs. ( = 440 lbs. Eng.) 
of guano per English acre, corresponded to the full measure 
of farm-yard manure usually applied ; this gives twenty 
pounds of guano for one of the plots. A good sample of 
guano was selected for the experiments, and on being sub- 
mitted to analysis, was found to consist of 14-53 water, 
88*88 ash, and 52*10 organic matter, of which 15*89 was 
ammonia. Twenty pounds of this guano, therefore, con- 
tained 8*07 lbs. of ammonia. In the ammonia salts used, 
analysis gave in 



Carbonate of Ammonia . . . 29-84 per cent. Ammonia. 
Phosphate " ... 21-96 " " 

Nitrate " ... 19-11 » " 



In correspondence with this percentage of ammonia, 
there were applied to two of the plots, I. and Y., 10|- Ba- 
varian pounds ( = 18 lbs. Eng.) of carbonate of ammonia ; 
to two others, II. and YI., 7^ lbs. ( == 9 lbs. Eng.) of nitrate 
of ammonia ; to two others, III. and YII., 12 lbs., ( = 14| 
lbs. Eng.) phosphate of ammonia. Two plots, lY. and 
YIII., received each 12 lbs. ( — 14| lbs. Eng.) of crystal- 
lised sulphate of ammonia ; another, 20 lbs. ( = 24-| lbs. 
Eng.) of the analysed guano. The plots, Y., YI., YIL, 
YIII., received each at the same time 8080 grm. ( = 6| Ibj. 
Eng.) of common salt. I will here communicate these ex- 
periments in full, as they offer other points of interest, in 
addition to the action which must be ascribed to the com- 
mon salt. 

Produce of barley (grain and straw), from the four plots 
manured with ammonia salts alone : — 



46 



THEOKETICAL AND PRACTICAL AGRICULTURE. 



Grain. Straw. 

grm. lbs, Eng. grm. lbs. Eng. 
L . . . = 6335 = 14-0 16205 = 35-6 

n = 8470 = 18-6 16730 = 36-8 

in. . . . = 7280 = 16-0 17920 = 39-5 

IV. . . . . = 6912 = 15-2 18287 = 40-2 

The umnanured plot gave= 6825 = 150 18375 = 40-4 

Produce of harley (grain and straw) from four plots 

manured with ammonia salts and common salt: — 



V. 

VI. 

VIL 

VIII. 



Grain. 

grm. lbs. Eng. 
14550 = 320 
16510 = 36-3 

9887 = 21-7 
11130 = 24-5 



Straw. 
grm. lbs. Eng. 
27020 = 59-5 
36645 = 80-6 
24832 = 54-6 



27969 



61-5 



Increase of produce in plots V. to YIII., manured with 
common salt and salts of ammonia, above that of plots I. 
to lY., manured with salts of ammonia alone : — 

Grain. Straw. 

grm. lbs. Eng. grm. lbs. Eng. 

V. . . . = 8255 = 18-2 10814 = 23'8 

VI = 7770 = 17-0 19915 = 43-8 

VIL . . . = 2607 = 5-7 6912 = 15-2 
Vin. . . . . = 4218 = 9-3 9782 = 21-5 



In instituting experiments in practical agriculture with 
manures, the increase of crop is generally the only object 
kept in view. If this object be attained, the experiments 
are said to be successful. In this sense, the above experi- 
ments, both with and without common salt, are unsuccess- 
ful; for the returns scarcely reach average crops. The 
object with which they were made was not, however, to 
obtain a greater crop than the average, but to investigate 
the action of the salts of ammonia alone, and with the 



THEORETICAL AND PRACTICAL AGRICULTURE. 47 

addition of common salt. In this respect they agree suffi- 
ciently to banish all doubt as to the physiological import- 
ance of common salt to the Bogenhausen fields. In every 
case the crop was increased by the addition of common 
salt. Common salt when used with carbonate of ammonia, 
doubled the produce of grain ; and with nitrate of ammonia, 
it raised the return of corn 90 per cent., — and of straw 120 
per cent. 

As the mixture of nitrate of ammonia and common salt 
contains the elements of nitrate of soda, a counter experi- 
ment with the latter salt on a plot of the same field, made 
at the same time, is of much interest. The plot manured 
with 16 lbs. (= 19f lbs. Eng.) of nitrate of soda, gave 
12320 grm. (= 27 lbs.) grain, and 82480 grm. (= 71i lbs.) 
straw ; and by the addition of 5^ lbs. (= 6f lbs. Eng.) of 
common salt, the grain increased to 17920 grm. {= 39|- 
lbs.), and the straw to 85780 grm. (= 78f lbs.). Common 
salt had, therefore, also increased the action of Chili salt- 
petre. A mixture of these two salts produced a still 
higher yield of grain, than a mixture of common salt 
and nitrate of ammonia, which contained the same pro- 
portion of nitrogen. The experiment with 20 lbs. (= 24f 
lbs.) of guano, on a plot of the same size, gave 17200 
grm. {= 88 lbs.) grain, and 83820 grm. (= 73^ lbs. 
straw. 

It is quite certain, that in the action of the guano, which 
produced the crop next highest after the Chili saltpetre, an 
unmistakable part was played by the ammonia contained 
in it. On the other hand, however, the experiments with 
carbonate and nitrate of ammonia show, that a quantity of 
ammonia, or nitrogen, equivalent to that in 20 lbs. of 
guano, and employed under the same conditions, was 
almost without effect. 

I will not, by further pursuing this subject, weaken the 



48 THEORETICAL AND PRACTICAL AGRICULTURE. 

significance of the most important fact brought out by 
these experiments with the salts of ammonia, viz., that 
common salt, in reality, exercises a favourable action on 
the growth of straw plants in the Bogenhausen fields, and 
increases the mass of vegetable matter in them. 

This fact is indeed not new in agriculture ; but in a num- 
ber of cases, in which common salt has been shown to be a 
useful addition to other manures, its action has not been 
sufficiently distinct and decided ; and it is a rule in natural 
inquiries that a fact must first of all be firmly established, 
before we proceed to seek its explanation. 

The action of common salt is evidently very similar to 
that of the salts of ammonia and nitrate of soda ; but if we 
refer the effect of these last two substances to their nitrogen, 
because ammonia and nitric acid are food for plants, then 
this explanation will not hold good for common salt. For 
neither this salt nor chlorine enters as an element into the 
structure of plants, and it cannot be asserted that either of 
them is necessary, although both are frequently met with 
as constituents of the ashes of plants. 

The most recent observations on the comportment of the 
soil towards the food of plants show how slight is the 
knowledge we possess of their mode of nourishment, and 
of the part which the soil, by its physical condition, plays 
in it. The comportment of the salts of ammonia, of 
chloride of sodium, and of nitrate of soda, towards the 
earthy phosphates in the soil, may perhaps assist us in 
throwing some light on their action, or on one of their 
actions, on the growth of plants. 

Like carbonic acid water, the sulphate, as well as other 
soluble salts of ammonia, possesses the property of render- 
ing the earthy phosphates soluble in water. 

We know of no other way in which the earthy phos- 
phates are dispersed through the soil than by means of 



THEORETICAL AND PRACTICAL AGRICULTURE. 49 

carbonic acid water. If it is true that one of the chief 
effects of humus, or the decaying remains of plants in soils 
or in manures, consists in its forming a source of carbonic 
acid, with which the air and water in the ground is en- 
riched ; if it is also true that this carbonic acid water ren- 
ders the earthy phosphates soluble, and thus contributes to 
their distribution in the soil, then there can be no doubt 
that the salts of ammonia, which possess the same solvent 
property, can in this respect replace the organic matters, 
and thus exert an equally favourable influence on the 
growth of plants. 

The same solvent property is also possessed among the 
salts of soda by Chili saltpetre and common salt. It has 
been recently shown that these two salts, even in the most 
dilute solutions, dissolve earthy phosphates to a very appre- 
ciable extent, and that consequently they must play a part 
in the process of the nutrition of plants, similar to that 
which is ascribed to carbonic acid water (to the humus) and 
to the salts of ammonia. 

From direct experiments it appears, that 100 kilo (= 220 
lbs.) of sulphate of ammonia in solution in 45,000 litres 
(= 9,900 galls.) of water can dissolve 8600 grm. (=7*9 lbs.) 
of bibasic phosphate of lime (POg, 2CaO, aq.) such as 
exists in bones that have been acted on by sulphuric acid ; 
or, in other words, 100 lbs. of sulphate of ammonia in 
4,500 gallons of water — dissolve nearly 4 lbs. of phosphate 
of lime. In like manner 100 lbs. (=123 lbs. Eng.) of com- 
mon salt, in 50,000 litres (= 11,000 galls.) of water, dis- 
solve 3,300 grm. (= 7-J lbs.) of bibasic phosphate of lime ; 
and 100 kilo. (= 220 lbs.) of nitrate of soda, in 83,400 
litres (= 7,848 galls.) of water, dissolve 2,630 grm. (= 5f 
lbs.) of the same phosphate. 

Tribasic phosphate of lime (POg, 8CaO) is much less 
soluble in these fluids. 

3 



60 



THEOEETICAL AND PKACTICAL AGRICULTUKE. 



100 kilo. (220 lbs.) of 



Sulphate of ammonia, 

Common salt 

Nitrate of soda 



In solution in water in 



54,000 litres (=11,880 galls.) 
50,000 " (=11,000 " ) 
33,300 " (= 7,326 " ) 



Dissolve of tribasic 

phosphate of lime, 

POs, 3 CaO. 



3400 -grm. ( = 7^ lbs.) 
1500 " (=3i " ) 
1200 '' (=2^ " ) 



The seeds of the cereals, particularly wheat, contain 
phosphate of lime, and in preponderating quantity phos- 
phate of magnesia. In many kinds of wheat the quantity 
of phosphate of magnesia is four times, often ten times, 
greater than that of the phosphate of lime ; and in like 
manner in the grain of rye, oats, and barley, the magnesia 
salt exceeds very greatly the phosphate of lime. These 
proportions are so constant that they cannot be ignored in 
the cultivation of these plants. The comportment of the 
salts above-mentioned towards phosphate of magnesia and 
ammonia, and phosphate of magnesia, appears, therefore, 
of special interest. 



100 kilo. (220 lbs.) of 


In solution in water, in 


Dissolve of phosphate 

of Magnesia, PCs 

3MgO. 


Nitrate of soda 

Common salt 


33,300 kilo. (= 73,260 lbs.) 
50,000 " (=110,000 ") 


2160 grm. (=4f lbs.) 
3790 " (=8^ " ) 


The solubility in the same fluids of phosphate of magne- 
sia and ammonia is still greater. 


100 kilo. (220 lbs.) of 


In solution in water, in 


Dissolve of phosphate 

of magnesia and 

ammonia, PO5. 2 MgO, 

NH4O. 


Sulphate of ammonia. 

Common salt 

Nitrate of soda 


33,300 litres (= 7326 galls) 
50,000 " ( = 11,000 " ) 
33,300 " (= 7326 " ) 


41 13 grm. (= 9 lbs.) 
6170 '* (=13| " ) 
4655 " (=10i " ) 



THEORETICAL AND PRACTICAL AGRICULTURE. 



51 



The quantity of the earthy phosphates taken up by the 
above fluids does not rise in proportion with the amount 
of salts in solution, but rather on the contrary with the 
dilution of these fluids."^ 

It is quite conclusive from these facts, that water con- 
taining a very small quantity of common salt, nitrate of 
soda, or a salt of ammonia, acquires thereby the power, 
(which alone it does not possess, or only in a slight degree) 
of dissolving phosphoric acid, in the form of earthy phos- 
phates. These feeble solutions, therefore, react towards 
earthy phosphates like solutions of carbonic acid in water. 
100 kilo. (=220 lbs.), for example, of sulphate of ammonia 
produce the same solvent effect on phosphate of lime as 
4720 litres {= 1038i galls.) of carbonic acid in solution in 
water; and 100 kilo, of common salt dissolve as much 
phosphate of magnesia and ammonia as a watery solution 
of 3456 litres (= 760J galls.) of carbonic acid. 

Direct experiments prove, that a very dilute solution of 
the same salts, take up phosphoric acid from a soil which 
contains earthy phosphates in excess, and that this dissolved 
acid is again given up by this solution to a similar soil 
which is not already saturated with phosphoric acid. 

If we submit to a close scrutiny the comportment of the 
salts of ammonia, nitrate of soda, and common salt towards 
soils, we find that not one of these salts acts in the same 
form in which it has been added to the ground. 



*1000C. a of fluid, con- 
taining at 57° F. 


Dissolve of PCs. 2MgO, 
NH4O. 


For 1 grm. of salt. 


2-2 grm. NH4OSO3 
3. u 

10- *' " 


76-7 mLIligrrQ. 
113-0 " 
147-0 " 


34-9 milligrm. 

37-6 

14-7 " 



52 THEORETICAL AND PRACTICAL AGRICULTURE. 

The salts of ammonia are immediately decomposed by 
the soil ; the ammonia is retained, whilst the acid enters 
into combination with lime, magnesia, alkalies, or, in short, 
with any basic substance in immediate contact and capable 
of combining with it. 

The action of these salts is therefore of a two-fold nature. 
On the one hand, they enrich the soil with ammonia ; on 
the other, their acid gives rise to new compounds which 
come into operation. The alkalies and alkaline earths 
which combine with the acid acquire thereby a greater 
degree of solubility, and are more readily diffused through 
the soil. If the ground is rich in magnesia or lime, the 
salts of these bases are formed ; but their influence, with 
the exception of that of gypsum, on certain plants cannot 
be estimated very high. The use of sal-ammoniac, instead 
of sulphate of ammonia, gives rise to chloride of magne- 
sium, and chloride of calcium, which act rather unfavoura- 
bly than otherwise on vegetation. That salts of these 
bases are generated by the action of soils on salts of ammo- 
nia, and that the new salts exert no particularly favourable 
influence on the increase of produce, are facts on which no 
doubt can rest. 

If, however, portions of the soil containing in some 
places phosphate of lime or of magnesia in the form of 
coarse grain, or powder, or bone earth, come in contact 
with these ammoniacal fluids, then there follows solution 
of these earthy phosphates, and their consequent diffusion 
through the soil. 

Potash salts resemble those of ammonia in the rapidity 
of their decomposition in contact with soils ; but the com- 
portment of soda salts is quite different. 

On slowly filtering a solution of nitrate of soda (contain- 
ing one-fifth per cent, of salt) through an equal volume of 
Bogenhausen loam, half of the salt passes through unab- 



THEORETICAL AND PRACTICAL AGRICULTURE. 53 

sorbed, whilst the other half is converted into nitrate of 
lime and nitrate of magnesia. Under the same circum- 
stances three-fourths of a solution of chloride of sodium 
remain undecomposed. 

If, therefore, a field is manured with nitrate of soda or 
common salt, and the soil becomes saturated with a dilute 
solution of these salts formed by rain, a great portion of 
them will remain unchanged in the ground, and must exer- 
cise on the moist soil an action which, though in itself 
feeble, becomes powerful by its continuance. 

Like the salts of ammonia, or a watery solution of car- 
bonic acid produced by the decay of organic matter in 
manures, a solution of these salts, wherever they come in 
contact with spots containing accumulations of earthy phos- 
phates not fixed by the soil, must become saturated with 
these phosphates, and thus convert them into a condition 
in which they can be diffused through the ground. If the 
earthy phosphates, when thus diffused in solution, come in 
contact with other portions of soil not yet saturated with 
these salts, those portions absorb and fix these earthy phos- 
phates, and the chloride of sodium or nitrate of soda 
retains, a second time, or more frequently, the power of 
exercising the same solvent and distributing action over 
the earthy phosphates until the ultimate and complete con- 
version of the chloride and nitrate into a lime or magnesia 
salt. 

When we consider how much the fertilising effect of 
bone earth is increased by the greater solubility and capabi- 
lity of distribution in the soil communicated by the action 
of sulphuric acid, we cannot too highly estimate the signifi- 
cance of the properties, just described, of the salts of ammo- 
nia, chloride of sodium, and Chili saltpetre. 

The most abundant application of earthy phosphates in 
coarse powder, can in its effects bear no comparison with a 



54 THEOKETICAL AND PRACTICAL AGRICULTURE. 

much smaller quantity which, in an infinite state of divi- 
sion, is dispersed through every portion of soil. A rootlet 
requires at the spot where it touches the soil a most minute 
amount of food ; but it is necessary to its functions and its 
very existence, that this minimum be found exactly at this 
spot. For if the food of plants be not soluble in water, 
then is any excess at any other spot as valueless to the func- 
tion of nutrition of this rootlet as if it did not exist at all 
in the soil. Now, the salts of which we have been speak- 
ing, possess the property of conveying these elements of 
food from the spot in which they exist in superabundance 
to others in which there is a deficiency ; and even though 
their elements contributed in no way directly to the pro- 
cess of nutrition, yet, these salts must nevertheless exercise 
a marked influence on the increase of produce. 

When the sulphate of ammonia and Chili saltpetre have 
been completely transformed into lime and magnesia salts, 
and the chloride of sodium into chloride of calcium and 
chloride of magnesium, this action then ceases ; and a second 
dose of these salts is then necessary to reproduce the action. 

If the effect of the salts of ammonia depends on the am- 
monia, we can scarcely comprehend why, after a large 
application of them, that portion which has not acted 
during the first year should not in the second come into 
operation, since this latter portion is presented in the soil 
to plants in the same form as the portion which produced 
its effect during the first year. 

Sulphate of ammonia produces on alkaline silicates a 
reaction similar to that on earthy phosphates. If this salt, 
in very dilute solution, is brought in contact with soil satu- 
rated with silicate of potash, and which does not give up a 
trace of its potash to water alone, it instantly dissolves a 
certain quantity of this alkali, which may be easily detected 
by the ordinary re-agents. 



THEORETICAL AND PRACTICAL AGRICULTURE. 55 

It is evident that the agriculturist, by the proper appli- 
cation of the chemical action of common salt, Chili saltpe- 
tre and ammonia salts, accomplishes the same object as by 
the mechanical operation of ploughing, and by the action 
of the atmosphere in fallow. 

We should be committing an error, if, judging from 
similarity of solvent properties, we concluded that common 
salt must have the same effect as a corresponding quantity 
of nitrate of soda. We know that, as a rule, in these cases, 
the common salt is converted into chloride of calcium, and 
the Chili saltpetre into nitrate of lime ; and the experi- 
ments of Kuhlmann have taught us, that chloride of cal- 
cium by itself is absolutely ineffective, or rather is hurtful 
in the cultivation of plants, whilst nitrate of lime contri- 
butes materially to the increase of a hay crop. ISIitrate of 
soda, consequently, acts favourably in two ways ; chloride 
of sodium only in one. Further, land plants can bear a 
considerable quantity of nitrates of soda in the soil, whilst 
chlorine compounds, beyond a certain very narrow limit, 
are decidedly hurtful. 

We designate as manures all substances which increase 
the produce of our fields, without knowing whether many 
of these may not simply act, by rendering the food already 
existing in the soil more capable of absorption and assimi- 
lation. The simple fact of their favourable influence on 
vegetation, is not yet a proof that they have acted directly 
as food. We compare the work which the plough performs, 
to the mastication of food, for which nature has provided 
animals with a particular instrument ; and, as may be seen 
from the experiments described above, many substances, 
such as common salt, nitrate of soda, and ammonia salts, 
independently of the action which is due to their own ele- 
ments, play a peculiar part, which may be compared to the 
digesting action of the stomach, and in which they can 



56 THEORETICAL AND PRACTICAL AGRICULTURE. 

partly replace eacli other; and inasmucli then as they pre- 
pare the food existing in the soil for the process of nutri- 
tion, and render it more fit for assimilation, they must 
necessarily exert a powerful influence on the growth of 
plants. 

We can now understand why these salts exercise a 
favourable action in the cultivation only on certain soils, 
and why on a second or third application of them, the same 
effect is only partially, or not at all reproduced. 

An agriculturist in possession of fields containing abund- 
ance of phosphates, but unequally distributed through them, 
would, were all other conditions the same, undoubtedly 
increase the activity of these phosphates, and thereby aug- 
ment the produce of his fields, if he possessed the means 
of withdrawing the basic phosphates from the soil and 
restoring them in the form of superphosphate. These 
means he actually employs, when he manures his fields 
with Chili saltpetre, ammonia salts, or chloride of sodium. 



LETTEK V. 

No free Ammonia in the Soil — The amount of Food obtained from the soil 
by plants is in proportion to the absorbent Root-surface — The early deve- 
lopment of Roots due to the accumulation of Nourishment in the surface 
soil — Estimations of the quantity of Ammonia in our cultivated fields — A 
deficient crop not due to the Absence of Ammonia in the soil — Experi- 
ments with salts of Ammonia; the crops only slightly increased thereby — ■ 
Increase of produce due to accompanying Minerals —Experiments of Lawes 
and Kuhlmann with salts of Ammonia, &c. — The fertility of a field depend- 
ent on the sum of the Mineral matters in it — The activity of these Minerals 
increased within a given time by the Salts of Ammonia — The soil more 
rapidly exhausted by their use unless there is a restoration to it of the 
removed Mineral matters. 

The soil contains a certain quantity of nitrogen in the form 
of ammonia and of nitrogen compounds derived from plants 
and animals. 

The observations of Thomson and of Huxtable, and par- 
ticularly the valuable memoirs of Way, have established 
the fact, that the carbonate of ammonia of rain water and 
of manures, and that existing in ammonia salts, are absorbed 
and so firmly fixed by the soil that no free ammonia can 
be present in it. As neither pure nor carbonic acid water 
can withdraw this fixed ammonia from the soil, it is self- 
evident that, in the nutrition of plants, the rootlets must 
extract it directly from the soil. 

If we now imagine that plants receive all the nitrogen 
they require for their development not from the air but 
from the soil, it is clear that every portion of soil must con- 
tain the necessary quantity of ammonia or nitrogen for their 
vital processes; and plants would not attain their maxi- 

3^ 



58 THEORETICAL AND PRACTICAL AGRICULTURE. 

mum development, if they found in those portions less 
than the roots could absorb and the plant appropriate. 
Were all other conditions for the formation of grain pre- 
sent, they would then produce a smaller quantity, or grain 
of a lighter weight. 

The productiveness of a field, in so far as it is dependent on 
nitrogen, would be in proportion to the sum of this element 
contained in the soil, and to that portion of this sum which 
is present in each transverse section of the soil from the 
surface downwards. In whatever spot the rootlets cannot 
find nitrogen, they would therefore at that spot absorb none. 

From two fields, containing from the surface downwards 
the same quantity of nitrogen, and supposing all the other 
conditions of growth to be given, it will be found that two 
plants will receive unequal quantities of nitrogen, if their 
absorbent surface of rootlets is unequal in extent. The 
plant with double extent of absorbing root surface will take 
up twice as much nitrogen as the other. This proportion 
holds good for all the elements of food in the soil. 

From a field which contains only half the quantity of 
food which is present in another, a plant with a double pro- 
portion of rootlet surface will receive as much nourishment 
as a plant with only half the rootlet surface obtains from 
the second field. 

These propositions are self-evident, and may afford an 
explanation in many cases of one of the leading effects of 
manures on our fields. For, an accumulation of nourishment 
in the upper layer of the field enables plants, during the first 
period of their development, to send out ten-fold, perhaps 
a hundred-fold more absorbing rootlets than they otherwise 
would have done, and their later growth will be in propor- 
tion to the greater number of rootlets thus gained, by which 
they are enabled to seek and appropriate the food distributed 
sparingly throughout the deeper layers. 



THEORETICAL AND PRACTICAL AGRICULTURE. 59 

We possess as yet no investigation of the number of 
rootlets and the extent of their absorbing surface in our 
cultivated plants, and cannot therefore with any degree of 
certainty fix the quantity of ammonia which must neces- 
sarily be present in each transverse section of soil to satisfy 
the full requirement of nitrogen in the different classes of 
plants. 

If we now accept, on the grounds mentioned in the next 
letter, that each square millimetre of the transverse section 
of a field must contain -J a milligramme of ammonia, in 
order to furnish to the rootlets of a wheat plant all the 
nitrogen which it requires for its full growth, it follows that 
10,000 lbs. (or 0*12 to 0*13 per cent.) of ammonia must be 
present in the soil of a hectare (2^ acres) of land within the 
depth reached by the chief roots. 

If we compare with the above the amount of ammonia 
or nitrogen, ascertained with certainty by numerous analyses 
to exist in the soils of different countries, it appears that a 
depth of even ten inches of the greater number of our cul- 
tivated fields famishes much more than this quantity. 

As our cultivated plants undoubtedly absorb through 
the leaves as much nitrogenised food in the form of ammo- 
nia and nitric acid from the air as well as dissolved in rain 
and dew, as uncultivated plants which receive no nitrogen- 
ised manure from the hands of man ; we can therefore 
conceive that the agriculturist will seldom have to seek the 
reason of his poor crops in a deficiency of ammonia or 
nitrogenised food alone, and that he must first of all direct 
his attention to certain other conditions in order to improve 
his harvest. 

A knowledge of the quantity of ammonia or nitrogen in 
a soil is, therefore, not sufiicient to enable us to judge of 
its facility or capacity for production. For, even though 
a better crop be obtained from many fields by the applica- 



60 THEOKETICAL AND PKACTICAL AGKICULTURE. 

tion of ammonia, on by far tlie great majority of others, the 
largest quantities of this food produce no effect ; because 
though the nitrogen must indeed be there, and takes part 
in the formation of the vegetable mass, yet it produces by 
itself no effect when the conditions are awanting which 
render it active. 

The experiments of Schattenmann made in 1843 in 
Alsace, are in this respect very instructive. Wheat fields 
manured by him with salts of ammonia gave a smaller return 
of grain than another portion of the same land which had 
received none of this manure. In like manner the experi- 
ments of the General Committee of the Agricultural Soci- 
ety of Bavaria in 1857 (see p. 46), show that the produce 
of barley in grain and straw was rather reduced than other- 
wise in a field to which carbonate of ammonia had been 
applied; and that the use of sulphate, phosphate, and nitrate 
of ammonia raised the produce only a few per cents. A 
quantity of guano containing the same amount of ammonia 
as these salts gave on the same field three times as much 
grain, and twice as much straw as the unman ured land. 

It is obvious that the proximate cause of the powerful 
action of the guano in this case must be sought for in those 
matters which in it accompany the ammonia ; for, as we 
have just stated, a quantity of ammonia equal to that of 
the guano produced no marked effect on the same field, in 
the same year, and with the same kind of crop. 

It is clear that a field which either originally contained, 
or has had added to it, a sufficient quantity of the substances 
that accompany ammonia in guano, would, on the subse- 
quent application of the salts of ammonia, produce an 
equally good crop as it would have done with the guano, 
and better than would have been the case without the 
aid of the ammonia. In such a case, however, it would be 
a hasty conclusion to ascribe the higher return to the action 



THEOKETICAL AJ^D PRACTICAL AGRICULTURE. 61 

of the ammonia alone, because in tlie years of greater 
increase ilie salts of ammonia had been exclusively used. 

The experiments of J. B. Lawes, in the years 1844 to 
1855, give practical proofs of the truth of this view. He 
manured a wheat field with superphosphate of lime (560 
lbs. per acre), and with silicate of potash (220 lbs.), and in 
the eleven following years only with ammonia salts (sul- 
phate of ammonia and chloride of ammonium) and reaped 
on an average from it a half more grain and straw than 
from another piece of unmanured land of the same 
size which, during the same years, had been sown with 
wheat. 

These results fully agree with those of Kuhlmann's ex- 
periments in 1844 to 1846, with salts of ammonia on a 
meadow. 

From a meadow which had been manured with sal ammo- 
niac, he obtained an increase of 645 parts of hay for every 
100 parts of the salt employed. In the same year, from a 
second meadow, to which sal ammoniac had been also 
applied, but with the addition of phosphate of lime, he 
reaped 1666 parts of hay for every 100 parts of sal ammo- 
niac; consequently the produce was 2l times more than 
was obtained without phosphate of lime. 

The importance of the addition of fixed mineral food to* 
the increase of crops, and to the duration of the fertility of 
our fields, will at once be evident to the most prejudiced i 
from another series of experiments by Lawes. 

During the period that the experiments already mentioned 
were in progress, Lawes had applied, on a third field, for 
three years, fixed mineral matters, and for nine years, salts 
of ammonia ; in 1846 it remained unmanured. This field 
had, therefore, received two applications of ammonia salts 
less, and two of mineral manures more than the second 
field. 



62 THEOEETICAL AND PRACTICAL AGRICULTURE. 

The following was tlje produce per acre of tlie three 
fields : — 

Grain and Straw. 

I. Unmanured field produced 34,272 lbs. 

II. Field manured 1 year with mineral substances, and ) ^^ 

11 years with salts of ammonia . . . f ' 
III. Field manured 3 years with mineral substances, 
and 9 years with salts of ammonia 



55,704 



Although the third plot had received above 700 lbs. of 
ammonia salts per acre less than the second, its produce 
had nevertheless increased by half a crop. These facts 
show in the most undoubted manner, that even on ground 
so rich in the fixed constituents of food for wheat, as to 
furnish during twelve continuous years, without any ma- 
nure, a yearly medium crop of 2856 lbs. of grain and straw, 
the greatest supply of salts of ammonia, with an insufiicient 
replacement of the mineral substances removed in the crops, 
produced a smaller amount of grain and straw than when 
these minerals were more fully returned to the soil. They 
show further that the salts of ammonia as manure were 
rendered unnecessary exactly in proportion to the supply 
of fixed mineral substances ; for the smaller quantity of 
ammonia applied to the third field gave, not a correspond- 
ingly smaller crop, but on the whole a higher return than the 
larger quantity of this substance on the second field which 
had received mineral manure only in the first year. 

The effect of mineral substances as manure is apparent 
by comparing the produce of Plots 11. and III. in the dif- 
ferent years. 

In the year 1850 Plot III. had been manured for the 
third time with 300 lbs. of carbonate of potash, 200 lbs. of 
carbonate of soda, 100 lbs, of sulphate of magnesia, 200 lbs. 
of bone earth, 150 lbs. of sulphuric acid, and in the five 
following years had received only salts of ammonia. 



THEORETICAL AND PRACTICAL AGRICULTURE. 



63 



Plot II. had only once (1844) been manured with super- 
phosphate of lime and silicate of potash, and in the eleven 
following years with salts of ammonia alone. 

The produce of these plots from the year 1850 was the 
following : — 



I, Unmanured plot 


Produce of grain and straw In lbs. 


1851 


1852 


1853 


1854 


1855 


2710 
5036 

4985 

1000 
1850 
1800 


2457 
4107 

4162 

1000 
1630 
1690 


1772 
2691 

3578 

1000 
1500 
2010 


3496 

5808 

7003 

1000 
1690 
2000 


2860 
3779 

5074 

1000 
1520 
1770 


II. In 1844 received mineral sub- 
stances, then up to 1855 • 

ammonia salts 

Ill In 1844, 1848, 1850, received ) 
mineral substances, then >• 
up to 1855 ammonia salts ) 

I .""^ 


II 


Ill 





We see from these numbers that Plot III., after receiving 
in 1850 a large supply of mineral manure, produced in the 
two following years no greater crop than Plot II., to which 
no such excess had been applied. From this absence of 
any marked effect from the mineral manure, the inexpe- 
rienced agriculturist might at once believe himself entitled 
to conclude that the plot already contained a sufficient quan- 
tity of these substances, and that, therefore, a further supply 
was unnecessary, and a piece of extravagance. These ex- 
periments, carried out with so much perseverance, prove, 
however, the unsoundness of such a conclusion. They 
show that not one particle has been inefficient, but that 
their action was only apparent after their distribution in 
the soil had been effected. They show that these mineral 
substances by themselves require a longer time to become 



64 THEORETICAL AND PRACTICAL AGRICUI PURE. 

active than when applied in the form of farm-yard manure, 
which supplies in its organic matter a source of carbonic 
acid as the natural solvent and distributor of its fixed con- 
stituents. The eftect of the mineral food exhibited in the 
increase of produce became apparent only in the fourth 
year (1853), and its continuance was still evident in the 
most visible manner in the sixth year. 

Whilst the ammonia salts increased the produce of the 
second plot (which had seven years previously received 
mineral manure) in the year 1853 one-half more than that 
of the unmanured plot, the produce of the third plot, with 
the same quantity of ammonia, was twice as high. In the 
year 1854, its produce exceeded that of the second plot 
by 31, and, in 1855, by 45 per cent. 

It is hardly possible to find another cause for the differ- 
ence between the two wheat fields manured with ammonia 
salts, than that the one was richer than the other in the 
mineral food for the wheat plant. Nothing can be more 
positive than that the produce of both fields bore no pro- 
portion to the quantity of ammonia applied. 

As the fixed mineral constituents incorporated with the 
third plot in the year 1850 must be regarded as the proxi- 
mate cause of its increased produce in the years 1853 to 
1855, there can be no doubt that the mineral matters (560 
lbs. superphosphate of lime, and 220 lbs. silicate of potash), 
applied in 1844 to the second plot, were equally the proxi- 
mate cause of the greater return obtained from it in the 
eleven following years than from the unmanured plot. 

With fields under conditions so identical as the experi- 
mental plots of Lawes, it cannot be supposed that the third 
plot could possibly have borne a larger crop in 1853, 1854, 
and 1855, than the second, had it not contained a larger 
amount of active mineral matters than the latter ; and had 
the sum of the active mineral substances in the second plot 



THEORETICAL AND PRACTICAL AGRICULTURE. 65 

not exceeded that in tlie unmanured, the increase and con- 
tinuance of the crops from this second plot would also have 
been impaired. 

It follows, therefore, as a natural consequence, that the 
crops from the unmanured plot are also proportional to the 
sum of the active mineral constituents in the soil. Had 
this sum been smaller, the deficiency would have been evi- 
dent in the diminution of the crops. With the increase of 
these mineral matters in the second field, the crops also 
increased by the aid of the salts of ammonia ; and a fur- 
ther quantity of these substances, applied to the third plot, 
was followed by a still larger crop from that plot, not- 
withstanding that it had received less ammonia than the 
second plot. 

It is further evident, from the above, that the crops, and 
the increase in them, were dependent on the sum of the 
mineral matters in the three plots, and on that portion of 
this sum, which had been rendered fit for absorption by 
the action of the salts of ammonia. Without the supply of 
fixed mineral substances to the second and third plots in 
Lawes' experiments, they would have been, after the lapse 
of a few years, precisely in the same condition as those of 
Schattenmann, from which there was obtained no increase 
of grain by the application of the salts of ammonia. When 
by the supply of salts of ammonia, or Chili saltpetre, the 
produce of corn and straw in a field is increased, the proxi- 
mate cause of this increase lies in the fact, that an addi- 
tional portion of the sum of the mineral substances in the 
field has been thereby rendered capable of assimilation by 
plants, and therefore become active. Without the presence 
of such an excess of mineral matter, the salts of ammonia, 
and Chili saltpetre, would not have been attended with any 
effect. 

A field, which, by manuring with these last-named salts, 



m THEORETICAL AND PRACTICAL AGRICULTURE. 

has produced a larger crop for one or more years is therebj 
impaired in fertility for f\iture crops : for it could retain the 
same degree of fertility only when the conditions of fertility 
remain the same ; just as it can become more fertile only 
by having those conditions of fertility increased. But, in 
the rich crops obtained by the use of ammonia salts and 
Chili saltpetre, the farmer removes from his field in the 
form of corn and straw, the mineral constituents of the soil, 
and the field is consequently less rich in these substances 
after the harvest than it was before. 

Experience teaches, that the produce of fields in the same 
district is very unequal, even though they contain the same 
quantity of decaying organic matter and nitrogen. From 
one meadow is obtained twice or thrice more hay than 
from a similar extent of another meadow placed in the 
same external conditions. An acre of clover land yields 
three or four times as much clover hay as an acre of an- 
other field. 

The causes of this unequal productiveness, are always 
and everywhere the same. 

The atmosphere conveys to two fields of equal surface a 
like quantity of carbonic acid and ammonia ; the more fer- 
tile field, nevertheless, yields two, three, or four times more 
carbon and nitrogen, in the form of hay or clover, than the 
other. It is evident, that in such a case, the cause of the 
increase lies in the soil, and not in the air. The more fer- 
tile field has furnished to the plants two, three, or four 
times more mineral food than the other: it contained a 
larger absolute quantity, or a larger available proportion of 
these substances. 

If we take two clover fields or meadows of unequal pro- 
ductiveness, in one of which there is accordingly present a 
larger quantity of mineral substances than in the other ; and 
if we suppose that the atmosphere supplies them in one 



THEOKETTCAL AND PEACTICAL AGRICULTUKE. 67 

year with two, three, or four times the amount of ammonia 
they usually receive, and that their produce is thereby in- 
creased, — it will be found that the increase of crop in the 
two fields will be always unequal. The return from the 
more fertile field will always be greater than that from the 
less fertile, and this in the same unvarying proportion ; for 
there has been no change in the sum of the conditions of 
fertility in the soils of the two fields. 

The increase in the fertility of a field by the application 
of ammonia, or its salts, necessarily presupposes the pre- 
sence of the conditions of this increase, and that a greater 
quantity of mineral matter has in a given time become 
active and capable of absorption. 

In every case the produce of a field and the duration of 
its fertility bear a fixed relation to the sum of the mineral 
substances in the soil. 

The greater or less abundance of the crop is proportional 
to the rapidity of the action of the mineral matters in a 
given time ; that is, to that portion of their total quantity 
which is annually transferred from the soil to the plant. 
Hence, if a field contains so much mineral matter that, 
without any supply whatever, it can yield in 100 years ex- 
actly 100 average (^. e. remunerative) crops of wheat, it 
may after this time possibly be still rich enough for another 
kind of crop ; but, in an agricultural sense, it is no longer 
a wheat field. 

If, by a more thorough mechanical preparation of the 
ground, or by chemical means, such as Chili-saltpetre, 
common salt, and salts of ammonia, the action of the avail- 
able mineral food be accelerated, the field will perhaps 
yield in 50 years as much grain and straw as it would have 
done in 100 years without these means, and in half the time 
it would be exhausted for the cultivation of wheat. 

By the use of such means the total produce of the field 



68 THEORETICAL AND PRACTICAL AGRICULTURE. 

is not increased, but only the quantity obtained in a given 
time. 

When the agriculturist loses sight of the conditions which 
determine the duration of his large crops, and relies on the 
effect of his labour, and on the application of Chili-salt- 
petre, salts of ammonia, and common salt, without at the 
same time taking care to replace the mineral substances 
removed by his crops, he is then speculating on the wealth 
of his field, of the extent of which he knows nothing, and 
can receive no information from others. He seizes before- 
hand on the produce of his fields, which in after years 
would undoubtedly have come to him ; and the only 
difference between him and a railway speculator is in 
general this : that the punishment for his foolish deeds 
inevitably overtakes him or his successors, which the specu- 
lator sometimes escapes by laying on the shoulders of others. 
The apparently remunerative employment of these means 
on many fields may last for a long time ere the agriculturist 
becomes aware of the inj ury he is doing himself by neglect- 
ing to return the mineral substances removed by his crops ; 
but the longer he continues by them to obtain these large 
crops, he is approaching nearer and nearer the limits at 
which they must cease. 



LETTER YI. 

The Amount of Carbonic Acid and Ammonia in the Air — The Balance of 
Organic Life — The Absorption and Assimilation of Food differs in Perennial 
and in Annual Plants— The mode of Growth of Perennial, Annual, and 
Meadow Plants — The quantity of ]S"itrogen in different Crops — Advantages 
of Nitrogenous Manures to Cereals is not in consequence of the failure of 
Nitrogen from Natural Sources — Organic and Nitrogenous Manures useful 
in Annual Plants with small absorbent Leaf and Root-surface — Effect of 
Nitrogenous Manures less marked in plants with large Leaf-surface — 
Supply of Ammonia in Manure not necessary to all Plants — G-reen Crops 
condense Ammonia from Natural Sources, and supply it in the excrement 
of animals to Corn-fields — The Nitrogen of Manures is thus indirectly 
obtained from the Air — The total quantity of Nitrogen from a manured 
Corn-field is not greater than from an unmanured meadow, but more time 
is required by the latter to collect it — Explanation of the good effect of 
Nitrogenised Manures on Annual Plants with small Leaf and Root- 
surface. 

The quantity of nourishment in the air, compared with 
its mass, is very small. 

If all the carbonic acid and ammonia dispersed through- 
out the atmosphere were collected in one stratum around 
the earth, and possessed the same density as at the surface 
of the sea, the layer of carbonic acid would be a little more 
than eight feet high, and that of the ammonia less than a 
quarter of an inch. Both are absorbed by plants, and the 
quantity of these gases in the atmosphere consequently 
diminishes. 

Were the whole surface of the earth a continuous mea- 
dow, from each hectare {2^ acres) of which 100 cwt. of hay 
was yearly reaped, these meadow plants would in twenty- 
one to twenty-two years exhaust the whole of the carbonic 



70 THEORETICAL AND PRACTICAL AGRICULTURE. 

acid in tlie air, and the whole living creation would at the 
same time come to an end. The air would no longer sup- 
port plants — that is, would no longer furnish them with an 
indispensable condition of life. 

We know that careful provision is made for the con- 
tinuous duration of organic life. Men and animals live on 
plants. All organised beings have only a passing and 
comparatively short existence. In the vital processes of 
animals, the food which nourishes them is transformed into 
its original form ; and the same change takes place with the 
bodies of all animals and plants after death : their com- 
bustible elements reassume the form of carbonic acid and 
ammonia. Both of these substances are gaseous, and return 
to the atmospheric sea, to serve once more for the forma- 
tion and development of a new generation, 

We thas see that the duration of organic life, in reference 
to the combustible elements forming the frame of plants 
and animals, is most intimately connected with the return 
of these conditions. The perpetual round of changes 
which the Creator has traced out for them, may, to a 
limited extent, be influenced by man, but it goes on with- 
out him. 

Wherever food in the form of corn and other produce 
of the soil abounds, there, men and animals will be found 
to consume it ; and these, in fulfilling the urgent natural 
law of self-preservation, continuously reconvert the food 
that supports them into its original elements. 

The atmosphere is never at rest : even in the absence of 
every breeze, it is in continual ascending and descending 
motion. The food which it gives up to plants at one spot 
is immediately replaced from another — from ever flowing 
sources. 

There is a marked difference between perennial and 
annual plants as regards the absorption and assimilation of 



THEORETICAL AND PRACTICAL AGRICULTURE. 71 

food. For though different species may possess the same 
capacity in this respect, yet the quantity necessary in a 
given time for their vital purposes is very unequal. To 
attain a maximum of growth in the shorter period of its 
existence, the annual plant requires more than the biennial, 
and the latter more than the perennial. 

Everything that tends to promote the growth of plants 
in general, exerts the same favourable influence on perennial 
plants as on biennials and annuals, but with this distinc- 
tion, that the development of the former is not in the same 
degree dependent on accidental and passing states of wea- 
ther. If the weather is unfavourable, the growth of the 
perennial is only retarded for a time : they can await a 
favourable change. Whilst thus waiting their increase is 
only for the time being arrested, but the annual plants 
reach the limit of their existence and die. 

In the first periods of the growth of perennial plants, 
the most powerful efforts of their vital energy are chiefly 
directed to the formation of roots. The atmospheric food 
received by the leaves is destined for the prolongation and 
ramification of these underground organs of absorption. 
This fact is most distinctly perceptible in young trees, 
which appear to grow so slowly in the first periods .of their 
existence, and afterwards so rapidly. When the roots have 
acquired a certain compass, their stem or stalk then 
increases in strength much more rapidly than at first, and 
the branches, shoots, and leaves, augment in number. 

In the growth of annual plants, the food is expended in 
two directions at the same time, viz., for the formation of 
the shoots, as well as of the leaves and roots ; they are, 
therefore, in reference to the equal supply and the proper 
proportion of their food, much more dependent than peren- 
nial plants on the condition of the soil, and on weather. 
The development of all parts of the annual plant must 



72 THEOKETICAL AND PRACTICAL AGRICULTURE. 

take place within a certain definite, relatively short period 
of time, and its growth can only be complete when the 
external conditions are equally favourable with those of 
the soil. 

The formation of underground suckers appears to be of 
the greatest importance to vegetation in the case of the 
perennial grass and meadow plants, because by them vege- 
tation is maintained. They appear mostly in cases where 
scarcity of food or external disturbing circumstances would 
endanger annual plants. Only the smallest portion of the 
plants on a thickly-covered plot of grass produces stems ; 
the greater part develops only tufts of leaves ; and a num- 
ber only underground suckers. A landscape essentially 
derives its character from perennial plants, which every- 
where take possession of the ground when not prevented 
by man. Cleared forest-land produces immediately in the 
succeeding year plants, many of which (as, for example, the 
raspberry) flower and bear fruit in the same year, and 
therefore could not have grown from seed. By continu- 
ously putting forth underground suckers, plants are kept 
for a number of years at a low state of growth, till ulti- 
mately the conditions for their complete development 
recur. 

The duration of vegetation on our meadows depends 
on this circumstance. The certainty of their produce 
under varying conditions of soil and weather, arises from 
the great number of plants, which are able to maintain 
themselves at this low stage of development. 

Whilst one species of plants grows, flowers, and bears 
seed above ground, a second and third collects below it the 
conditions for a similar future growth. The one seems to 
disappear, in making room for a second or third, until the 
conditions for its own growth again recur. By manuring 
with ashes we cause clover plants to shoot out from the 



THEORETICAL AND PRACTICAL AGRICULTURE. 73 

green sward. An abundant crop of French rye-grass 
showed itself when superphosphate of lime was applied, 
but not a straw of this grass was to be seen where no 
superphosphate fell. 

A wonderful provision of nature ensures, by this 
sequence and change, the continued existence of plants, 
which clothe the fields with perennial green. The agri- 
culturist, in adopting the rotation of crops in the cultiva- 
tion of the annual plants which supply the food of man 
and animals, but follows in this operation a higher law. 

The circle from which a perennial plant extracts its food 
enlarges from year to year ; if its roots find but little in 
one spot, its wants are supplied from another which is 
richer. Whilst the roots of annual plants die every year, 
perennial plants preserve theirs in a state of readiness to 
absorb food at every favourable opportunity. Many retain 
their stalks or stems, in which are stored up, for the future 
necessities of leaves and buds, the unconsumed portion of 
their food. Hence, perennial plants grow with luxuriance 
on comparatively poor ground, which will not yield annual 
plants without a supply of food from the hand of man. 

Annual plants cannot follow each other continuously on 
the same soil without exhausting it ; hence, in the rotation 
of crops, perennial plants come most advantageously after 
the annual, and vice versa. 

The nearer an annual plant approaches in its comport- 
ment to a perennial, the more independent is it of any 
supply of atmospheric food. So long as a plant puts forth 
fresh leaves, it exists and maintains its power of absorbing 
carbonic acid and ammonia from the atmosphere; and, 
during the continuance of this power, there is so much the 
less necessity for a supply of these substances from the 
soil. 

A pea plant which pushes out fresh leaves and blossoms, 

4 



74 THEORETICAL AND PRACTICAL AGRICULTURE. 

at the same time that its seeds are ripening, receives more 
combustible elements from the atmosphere, than a corn 
plant, whose leaves and green stem fade after the appear- 
ance of the flower, and with the ripening of the seeds, 
and consequently lose their power to absorb atmospheric 
food. 

Hence we can understand why organic substances which, 
in decaying, supply to the roots carbonic acid and ammo- 
nia, when applied at the proper time cause in one plant an 
increase of vegetable matter, and in the amount of seed, 
whilst the produce of another is scarcely increased by 
them. 

From an equal surface of land we obtain in different cul- 
tivated plants a very unequal amount of blood and flesh 
constituents, or nitrogen. If we designate by the number 
100 the quantity of nitrogen which is yielded by a field of 
rye in the form of grain and straw, we shall obtain from 
the same field — 

In Oats 114 

Wheat 118 

Peas 270 

Clover 390 

Turnips 4t0 

Accordingly peas, beans, and green crops in cultivation, 
yield more nitrogen than the cereals. Peas and beans give 
more than double, clover and turnips three or four times 
more flesh and blood constituents than wheat. Clover and 
turnips can yield on many fields this higher produce with- 
out receiving any nitrogen in manure. In the case of 
clover, the yield can be still further augmented by the 
application of ashes, and in that of turnips by superphos- 
phate of lime. 

In cultivation, nitrogenous manures prove particularly 
useful for cereals, though the growth of clover and root- 



THEORETICAL AND PRACTICAL AGRICULTURE. 75 

plants on many fields is also greatly promoted by tliem. 
In general, the luxuriant growth of green crops on fields 
which have received no nitrogenous manure shows, that the 
utility or necessity of these manures for cereals does not 
arise from a deficiency in the supply of nitrogen from 
natural sources, and cannot be explained by a supposed 
failure of this supply. The column of air floating above a 
clover and corn field offers to both plants the same amount 
of carbonic acid and ammonia, yet from the same soil from 
which the agriculturist has received a very poor return of 
nitrogen in the form of grain and straw, he obtains three 
or four times the quantity of nitrogenous constituents in a 
crop of a fodder plant. The same source of nitrogen was 
open to both plants ; there could, therefore, have been no 
deficient supply to the corn plant, since the clover drew 
from it its three and fourfold quantity. It is quite certain 
that a soil, from which a poor crop of corn has been 
reaped, will not be made to yield a greater quantity, even 
by the most abundant application of ammonia. 

The failure of the corn crop must therefore be owing to 
other circumstances, and the proximate causes must be 
sought for in the condition of the soil. 

On the other hand, it cannot be doubted, that two fields 
containing equal quantities of the fixed food of plants, are 
nevertheless unequally productive in cereals, if in one of 
them there exist more carbonaceous and nitrogenised organic 
matter than in the other. The field which is richer in 
organic matter produces a higher crop of com and straw. 
It is further certain that, if an equal quantity of the fixed 
constituents of food has been supplied in manure to two 
fields, but one of them has at the same time received in 
addition in organic matters a store of carbonic acid and 
ammonia, in general the latter will produce a larger crop 
of corn than the other. 



76 THEORETICAL AND PRACTICAL AGRICULTURE. 

This increase of produce under these circumstances (iu 
whicli the soil is supposed to be rich enough in mineral 
food and in carbonaceous and nitrogenous organic matter) 
takes place in the case of cereals as well as of other annual 
plants, with a scanty supply of leaves and limited ramifi- 
cation of roots ; and the reason of the utility, in such cases 
of organic and nitrogenised substances, is very evident. It 
lies manifestly in this, that the amount of nitrogenised 
products, which can be obtained from a given surface of 
such land, is in fixed proportion to the extent of leaf sur- 
face, or in general terms, to the organs of absorption, and 
to the time in which these organs are in a state of 
activity. 

If one plant possesses twice the extent of surface of 
leaves which exists in another, it will, during the same 
period of vegetation, extract double the quantity of nitro- 
gen from the air. 

Of two plants with equal extent of surface of leaves, and 
under similar circumstances, but with unequal periods of 
vegetation, one will yield a larger crop than the other, if 
with the same supply of food it has longer time for its 
absorption. By manuring his fields with nitrogenous sub- 
stances, the agriculturist exercises an immediate influence 
on the produce ; and the effect of these manures, through 
the nitrogen they contain, is in inverse proportion to the 
absorbing leaf and root-surface, and to the period of vegeta- 
tion of the crop. 

The effect of nitrogenous manures is less marked in 
plants with a large surface of leaves (as in peas, turnips), or 
which have a longer period of vegetation (as in meadow 
plants, clover) than in culmiferous plants. Ammonia is 
necessary as food to all plants, but a supply of it in 
manure is, in the agricultural sense, not useful to all culti- 
vated plants. 



THEORETICAL AND PRACTICAL AGRICULTURE. 77 

Experience has taught the agriculturist to make a dis- 
tinction in this respect. As a rule, he does not manure his 
clover field with nitrogenous matters, because the crop of 
clover is generally not thereby visibly increased, or only 
very slightly ; whilst he reaps a decided advantage in the 
increase of his produce by applying these matters to his 
corn fields. 

The agriculturist therefore makes use of green crops as a 
means of increasing the productiveness of his corn fields. 

Green crops, which thrive without nitrogenous manures, 
collect from the soil and condense from the atmosphere, in 
the form of blood and flesh constituents, the ammonia sup- 
plied from these sources. When the agriculturist feeds his 
cattle, sheep, and horses with these green crops, he obtains 
in their solid and liquid excrements the nitrogen of the 
fodder in the form of ammonia and highly nitrogenised 
products, and thereby a supply of manure for his corn 
fields. 

The ultimate source of the nitrogen with which the 
agriculturist manures his corn fields is invariably the air. 
Each year he carries away from his land a certain quantity 
of nitrogen in the form of fattened animals, corn, cheese, or 
milk : but his trading capital of nitrogen is maintained and 
increased, if he knows how to replace the deficiency by the 
cultivation of green crops in proper proportions. 

In the temperate zones, it is usually on the annual plants 
that man depends for his food ; and the problem which the 
agriculturist has to solve, is to obtain from his land in the 
form of annual plants as much food for man, as perennial 
plants furnish to animals from the same extent of surface. 
Nature takes care of animals which cannot take care of 
themselves ; whilst for the purpose of ensuring the means 
of his subsistence, man has been endowed with the power 
of making the laws of nature minister to his wants. 



78 THEORETICAL AND PRACTICAL AGRICULTURE. 

The best corn field, whicli has been manured, produces 
altogether no more blood and flesh constituents than a goc d 
meadow, which has received no nitrogenous manure. But 
the corn field without manure would have yielded a smaller 
amount of these constituents than the meadow. 

Whatever deficiency there is in the quantity of atmo- 
spheric food, taken up by corn plants within a given time 
from natural sources, to produce a maximum of corn and 
straw ; whatever amount of food the scanty supply of leaves 
has not the power of absorbing from the air during the short 
period of their existence, that portion the agriculturist sup- 
plies through the roots. 

The agriculturist thus supplements by manures the dif- 
ference between the amount of atmospheric food taken up 
in eight months by meadow plants, and that obtained by 
cultivated plants from the air during their more limited 
period of vegetation of four to six months ; and he thereby 
ensures to corn plants, during their shorter existence, as 
much nitrogen for assimilation as is furnished to meadow 
plants from natural sources. 

Hence the explanation which can be offered of the effect 
of nitrogenised manures and their advantages in certain cases 
is, that the agriculturist furnishes to certain plants, having a 
scanty supply of leaves and roots and a short existence, in 
quantity as manure, the nitrogen which they have not time 
to absorb from natural sources. 

But the agriculturist does not always apply the nitrogen 
with which he augments his crops in the form of the 
ammonia of rotting excrements of man and animals. He 
also employs frequently for this purpose other nitrogenous 
substances, as horn, dried blood, fresh bones, rape-dust, &c. 

We know that these substances, as well as all nitrogenous 
matters derived from man and animals, by degrees decay in 
the soil, and their nitrogen is gradually transformed into 



THEOKETICAL AND PRACTICAL AGRICULTURE. 79 

nitric acid and ammonia, and that the latter is absorbed and 
retained by the soil. 

In all cases in which ammonia as such produces favourable 
results on crops, these substances, so far as regards the 
nitrogen they contain, also act in the same manner. But 
their effect is more slowly produced, because they require, 
according to the greater or less facility with which they are 
decomposed in the soil, a certain time for the transformation 
of their nitrogen into ammonia. Dried blood and flesh, as 
well as the nitrogenous constituents of rape-cake, act more 
quickly than the gelatine of bones, and the latter more 
quickly than horn. 



LETTER YII. 

Salts of Ammonia increase the number of Roots and Leaves in the first period 
of the Growth of Plants ; hence the superior action of these salts in Spring 
— Circumstances which modify the production of Leaves, Flowers, and Roots 
— Circumstances under which Nitrogenous and Concentrated Manures are 
useful — Causes of the failure of plants continuously grown on the same Soil 
— Food of plants when too concentrated often exerts a deleterious Cliemical 
action — Provision in the Soil to prevent this action — Properties of Soils 
altered in cultivation by the removal of Mineral Matters from them, and by 
the increase of Organic Matters in them — The increase of Organic Matter 
frequently a cause of Disease — Finger and Toe disease ; its cure — Excess 
of soluble Silica and of hurtful Organic Matter in soils removed by Lime — 
Noxious Organic Matters arising from the continuous growth of Perennial 
Plants on Meadows removed by Irrigation. 

The experiments of Kuhlmann, Schattenmann, andLawes, 
agree in showing, that the salts of ammonia exert a most 
favourable influence on the evolution of straw and leaves ; 
and if this influence extends in like manner to the under- 
ground organs, the roots, then it ought to follow that the 
action of ammonia promotes the development of those 
organs destined for the absorption of food, and that these 
salts applied at the proper time increase the number of the 
leaves and roots. 

This circumstance explains the favourable action exer- 
cised in spring by ammoniacal manures, whilst in summer 
their influence under otherwise similar circumstances is 
trifling. 

If the plant, in fact, has produced during the first period 
of its growth a sufficient number of leaves and roots, an 
additional supply of ammonia can be of no great use to its 



THEOKETICAL AND PRACTICAL AGRICULTURE. 81 

further development, where the other constituents of food 
in the soil are not deficient ; for the leaves can now receive 
from the air the nitrogenous food necessary to the formation 
of seeds. In summer there is more watery vapour in the 
air than in the colder spring ; and as the quantity of ammonia 
in the air, according to the observations of all experimenters, 
increases with the temperature and moisture, plants must 
necessarily find more ammonia in the air in summer than in 
spring. We may as a rule hold, that in the colder seasons 
of the year, plants are more dependent on a supply of 
ammonia from the soil, than in the warmer ; or in other 
words, that the employment of nitrogenous manures in 
spring is most advantageous to plants. 

In England and Scotland it is the result of general ex- 
perience, that the earthy phosphates are not always suffi- 
cient for a good and certain crop of' turnips. When sown 
in May they require the addition of a nitrogenous manure, 
whilst, if this take place in the middle of June, they thrive 
generally as well with phosphates alone, as when combined 
with ammonia. 

We can hence tolerably well define the cases in which 
ammonia is hurtful ; for whilst nitrogenous manures pro- 
mote the growth of the leafy cabbage, they impede that of 
the roots of turnips. The latter plant is frequently ob- 
served to shoot out only stem and leaves when growing on 
spots upon which manure heaps have lain. Mangold-wurzel 
in a similar case produces the largest roots. The flowering 
time of these plants is delayed by this manure. 

To produce flower and seeds, it appears to be a necessary 
condition, in many cases, that the activity of the leaves 
and roots should reach a certain limit, — a period of rest. 
It is only from this period that the vegetative activity 
appears to take a decidedly new direction, and that the 
sap, when no longer required for the production of new 

4* 



82 THEORETICAL AND PRACTICAL AGRICULTURE. 

leaves and roots, is applied to the formation of flower and 
seed. 

With many plants want of rain, and of the consequent 
supply of food, limits the formation of leaves, and pro- 
motes the production of flowers. Dry and cool weather 
hastens the formation of seeds. In warm and moist cli- 
mates, the cereals when sown in summer bear little or no 
seed ; and root crops flower and bear seed more readily on 
a soil poor in ammonia, than on one rich in this substance. 

In the employment of nitrogenous manure, the agricul- 
turist must consequently have distinctly before him the 
object which he wishes to attain. He mast act with plants 
as with animals. When he wishes to fatten the latter, and 
at the same time to preserve their health, he gives them 
daily no more food than they can digest. 

Manures must always be of such a nature as to furnish 
plants with their suitable food at each period of their 
growth. Plants which have a longer period of vegetation, 
require consequently no supply, or, at least, a much smaller 
one of nitrogenous manures than those whose period of ex- 
istence is short. For such as possess the shortest period 
of vegetation, and which grow rapidly and with vigour, the 
concentrated manures are preferable to those which give 
up their active constituents only slowly. In dry localities, 
winter wheat thrives after clover without further manuring ; 
whilst, as a rule, the application of Peruvian guano or 
Chili-saltpetre (top-dressing) is most beneficial to wheat 
sown in spring. 

The continuous cultivation of the same plant on the 
same field, does not necessarily unfit this field for its pro- 
duction, if it is amply provided with the chemical condi- 
tions for the growth of the plant, and possesses physical 
properties of a right kind. If after the third or fourth 
year, the plant no longer thrives on such a field, the reason 



THEOKETICAL AND PRACTICAL AGRICULTURE. 83 

manifestly does not lie in any deficiency of its vital condi- 
tions (for we have assumed that these are present), but in 
the accumulation of causes which injure its healthy growth. 

The food of plants consists of chemical compounds, 
which, in virtue of their chemical properties, produce cer- 
tain effects on the substance of the cells and the most deli- 
cate portions of the frame of the leaves and roots, by which 
plants appropriate their food. Their chemical action in- 
creases with their quantity ; and if presented to plants be- 
yond certain limits, they sicken and ultimately die. 

In air in which free ammonia is present in excess, even 
though it be to only a most minute extent, many plants 
die as if struck with a poisonous blast. Carbonic acid acts 
in a similar way, though in a less degree ; and weak solu- 
tions of free alkalies or alkaline earths and their salts in a 
soil produce the same effect on other plants. 

In nature we find a wonderful provision exists in the 
chemical and physical properties inherent in the soil, for 
completely obviating the chemical action of the nutritive 
matters on the absorbent rootlets. Free ammonia, the free 
alkalies, and alkaline earths, are fixed by the soil, and with 
their loss of solubility they also lose those chemical pro- 
perties which are hurtful to plants. Plants can then select 
what is necessary to their existence, without any hindrance 
from extraneous influences which may endanger their pro- 
per growth. 

It is evident that the soil must possess such a neutral 
chemical character as the most important condition of the 
healthy structure and functions of the roots. The different 
species of plants require, however, special conditions for 
the growth of each. One species requires the constituents 
of fresh spring water; another flourishes only in bogs; 
others in carbonaceous and sour soils ; others, again, only 
in ground which abounds in alkaline earths. 



84 THEOKETICAL AND PRACTICAL AGRICULTUEE. 

By cultivation the cliaracter of tlie soil is modified, not 
only by the removal in crops of a portion of its active in- 
gredients, but also by the addition to it, by means of many 
plants, of a greater amount of carbon and nitrogen sub- 
stances, in the form of the remains of roots. The enrich- 
ment of the soil in organic matter appears to be a cause of 
disease and death to many plants. Clover and many of 
the turnip tribe will no longer grow on such a soil, and 
several species of grass quickly disappear from it. 

It has been frequently found in England that turnips, 
when grown on the same field at too short intervals, become 
subject to a peculiar disease, which manifests itself in an 
unusual development of the roots. Instead of a round, 
fleshy head, weighing several pounds, from which filament- 
ous roots spread out into the ground, the tap-root splits into 
a great number of hard, woody, stem-like roots of the thick- 
ness of a finger (finger and toe disease). This disease, which 
is owing to the peculiar character of the ground, is removed 
by a large dose of quick lime. It is certain, however, that 
the lime does not act in this case, because there was pre- 
viously a deficiency of it in the soil, for a supply of it to 
the field at seed time, like other manures, produces no 
effect, for the latter is apparent only after one or two years. 
To produce a favourable change in the quality of the field, 
the lime must manifestly penetrate to a certain depth, and 
this requires a considerable time. By the simple applica- 
tion of superphosphate of lime, to the complete exclusion 
of organic manures, Lawes succeeded in raising nine suc- 
cessive crops of turnips on the same land, and in the ninth 
year obtained 187 cwt. of roots per acre. 

Eain water, in slowly filtering through a soil rich in 
organic matter, extracts a substance which communicates a 
brown colour, and at times an acid reaction to the water. 
An addition of burnt lime to this soil destroys the solubility 



THEORETICAL AND PRACTICAL AGRICULTURE. 85 

of the organic matter in water, and its power of diffusion 
in the soil. Ttie lime decomposes the organic substances, 
and by its presence converts the process of putrefaction, 
which is hurtful to plants, into one of decay which is advan- 
tageous to them. 

The presence of organic matter in a soil rich in silicates, 
enables water in percolating through the soil to dissolve a 
much larger quantity of hydrated silicic acid than is con- 
ducive, in many plants, to the process of absorption taking 
place in the roots. Lime destroys this property, and, by 
its direct action on the silicate, potash is ultimately set free, 
and rendered fit for distribution in the soil. Sainfoin con- 
tinues to flourish on fields rich in lime. It is certain that 
the presence of the lime in such a soil is not advantageous to 
this plant, because it requires more lime for its vital pur- 
poses than other plants which flourish luxuriantly on land 
much poorer in lime ; but the canse for the necessity of this 
excess of lime must be sought for in the fact, that it destroys 
certain injurious matters which gradually accumulate by 
the continuous growth of this plant on the same soil. 

As a matter of course we understand, that, in a number 
of cases in which the same plant will no longer grow on 
the same soil, the cause just indicated is not alone in opera- 
tion, but deficiency of food generally, or in the proper pro- 
portions, must be regarded as the proximate cause of the fail- 
ure. The necessity for taking into consideration so many 
causes which impede or promote the growth of plants, 
makes the practice of agriculture one of the most difficult 
of pursuits. 

In fields bearing perennial plants, with roots which pene- 
trate to no great depth, similar injurious matters gradually 
collect, which are hurtful to the growth of future genera- 
tions of plants. The irrigation of meadows appears to 
accomplish the important object among others of removing 



86 THEOEETICAL AND PRACTICAL AGRICULTURE. 

these injurious matters by the oxygen and by the carbonic 
acid dissolved in the water, which penetrates the ground, 
and brings it into a condition similar to that produced by 
careful ploughing. An analysis of the water flowing from 
the meadow would probably show that it removes as much 
mineral matter and ammonia as it brings to it. We do not, 
of course, here speak of meadows to which liquid manure 
has been applied, or which have been irrigated with rich 
sewerage water from towns ; for in these cases two causes 
are in operation to augment the produce, one of which (a 
supply of mineral food and ammonia) is almost excluded 
in the case of spring and river water. 



LETTER Vni. 

The food of Land Plants is not absorbed by the roots from Solution, but from 
the Soil directly in contact with them — Hence the necessity for a uniform 
distribution of the food of plants in the soU, and for the great Ramification 
of their Roots — A field with much mineral food may be comparatively 
unproductive if it is not thoroughly mixed with the Soil — The roots of a 
crop diminish the mineral food in those portions of the soil in contact with 
them — Fertility is restored to those portions by ploughing and other 
mechanical means, which mix the soil and allow the roots to ramify freely 
— Reason of the value of Green Manures — Estimation of amount of mine- 
ral food in the soil to produce different Remunerative Crops — Law of 
Exhaustion in soils for different crops — Action of organic remains in the 
soil on the mineral constituents — Progress of diminution in Grain and Straw 
of cultivated crops, when the Ash Constituents are not restored to the soil, 
and when those of the straw alone are returned — Relation between the pro- 
duction of Leaves and of Grain — Relative proportions of mineral food 
required for Grain and for Root or Leaf-producing crops — The increase of 
Organic matter and Nitrogen in the soil by Green Crops, without the 
addition of mineral food, augments the produce of grain, but hastens the 
period of Exhaustion of the soil — Progress of the exhaustion of a soil by 
the cultivation of shallow and of deep rooting plants — The manner in which 
the Subsoil contributes to the prolongation of the fertility of land — 
Importance of the formation of large roots after germination — Exhausted 
fields in an agricultural sense — Fertility restored by manures — The nature 
of Manures — The part played by the Organic and Inorganic Matter of 
Manures — Farm-yard Manure. 

The culmiferous, turnip, and tuberous plants which the 
agriculturist cultivates, comport themselves in a most pecu- 
liar manner in the absorption of their mineral food. Whilst 
sea-plants receive their whole supply of these substances in 
a state of solution from the surrounding medium, the water 
which percolates through cultivated soils, brings to the 



88 THEOKETICAL AND PRACTICAL AGRICULTURE. 

roots of land plants none of the three most important and 
most essential elements of food, viz., phosphoric acid, pot- 
ash, and ammonia. Water alone withdraws from the soil 
none of these substances ; their passing into the organism 
of plants must therefore be directly effected by the organs 
of absorption in the ground, with the co-operation of water. 
The roots extract these substances from those portions of 
the soil, penetrated with water, which are in direct contact 
with their absorbent surfaces; and such portions of soil 
must contain the whole quantity necessary for the complete 
development of the plant, since the roots can receive none 
of them, except from the particles of earth with which they 
are directly in contact. 

If the food of plants in the soil cannot move towards the 
roots, it is evident that the roots must spread about to look 
for food. 

Plants cannot obtain from the soil more food than it 
contains. Further, its fertility is not to be measured by 
the whole quantity present in it, but only by that portion 
of the whole quantity which exists in the smallest particles 
of the soil. For it is only with such portions that the root- 
lets can come into close contact. 

A piece of bone weighing about 30,000 milligrammes 
(one ounce) in a cubic foot of earth, produces no marked 
effect on its fertility. But if these 80,000 milligrammes of 
phosphate of lime be uniformly distributed throughout the 
earth, it will suffice for the nourishment of 120 wheat 
plants. Ten thousand milligrammes of food, having a sur- 
face extent of 100 square millimetres, are within the same 
given time not more effective than ten milligrammes having 
the same surface extent. Of two fields with the same 
amount of food, one may be very fertile, and the other 
equally unfruitful, if the food is more uniformly distributed 
throughout the former than the latter. 



THEORETICAL AND PRACTICAL AGRICULTURE. 89 

The common plough breaks and turns up the soil with- 
out mixing it ; it only displaces, to a certain extent, the 
spots on which plants have already grown. But the spade 
breaks, turns, and mixes it thoroughly. 

A potato, turnip, or wheat plant cannot thrive on the 
spot in which the same kind of plant has grown in the pre- 
ceding year, if the portions of soil with which the rootlets 
were in contact, contain no more, or only an insufficient 
residue of food. The roots of the succeeding plants find in 
all these spots either no food or only a deficient supply. 
Every other spot contains more. 

As the smallest portions of food cannot of themselves 
leave the spot in which they are held firmly fixed by the 
soil, we can understand what immense influence must be 
exerted on its fertility by its careful mechanical division 
and thorough intermixture. 

This is the greatest of all the difficulties which the agri- 
culturist has to overcome. 

If a field is to produce a crop, corresponding to the full 
amount of food present in it, the first and most important 
condition for its accomplishment is, that its physical state 
be such as to permit even the finest rootlets to reach the 
spots where the food is to be found. The extension of the 
roots in every direction must not be obstructed by the 
cohesion of the soil. Plants with thin delicate roots cannot 
grow on a tenacious heavy soil, even with abundance of 
mineral food. These facts explain in a very simple manner, 
one of the many favourable effects of green manures on 
such soils, and enable us to understand the reasons of the 
preference given in many cases, by agriculturists, to fresh 
over rotten farm-yard manure. The mechanical condition 
of the ground is, in fact, remarkably altered by the plough- 
ing in of plants and their remains. A tenacious soil loses 
thereby its cohesion ; it becomes brittle, and more readily 



90 THEOEETICAL AND PRACTICAL AGRICULTURE. 

pulverized than by the most careful ploughing ; and, in a 
sandy soil, a certain coherence is introduced among its 
shifting particles. Each stem of the green manure plants 
ploughed in opens up by its decay a road by which the 
delicate rootlets of the wheat plant ramify in all directions 
to seek their food. With the exception of their combus- 
tible elements, the ground receives from the green manure 
plants nothing which it did not previously contain; and 
these of themselves would have no effect on the increase of 
the crop, without the presence in the soil of the necessary 
mineral food. 

None of the three most important constituents of food 
exists, by itself, in a soluble form in the ground, and none 
of the means employed by the agriculturist to make them 
available to his plants, deprives the soil of its power of 
retaining them ; or, if dissolved, of withdrawing them from 
this solution. The principal end gained by the means he 
employs is only an uniform distribution of the food 
throughout the soil, so as to put it within the reach of the 
roots of his plants. 

A 2^ acre field ( = 1 million square decimetres) of good 
wheat soil produces an average crop of 2000 kilo. ( = 4411 
lbs.) of grain, and 6000 kilo. ( = 11,028 lbs.) of straw; the 
two contain together 250 kilo. ( = 551 lbs.) of mineral sub- 
stances. Each square decimetre ( = 10,000 square milli- 
metres Or 15*5 square inches) of this field yields 250 milli- 
grammes ( = 3 "85 grains) of ash constituents to the plants 
growing upon it. Each square millimetre ( = '00155 
square inch), from the surface downwards, must contain a 
quantity of food corresponding to the wants of each indi- 
vidual rootlet. If the food is wanting in any one particular 
particle of the soil, then this portion cannot contribute to 
the nourishment of the plant. The amount of food in each 
portion of a transverse section of ground^ in each square milli' 



THEORETICAL AND PRACTICAL AGRICULTURE. 91 

metre from the surface doivnivards^ is the measure of its capacity 
for production. Each rootlet absorbs, according to its dia- 
meter, the food with which it comes in contact on its way 
downwards. 

If we suppose that the sectional area of the roots of the 
whole wheat plants which grow on a square decimetre 
amounts to 100 square millimetres, or that upon the same 
surface there exists a wheat plant with two or three stems, 
and with a hundred roots each of a square millimetre sec- 
tional area, then must each of these rootlets receive 2^ 
milligrammes of mineral food in order to supply the plant 
with 250 milligrammes. Each of the 10,000 square milli- 
metres ( = one square decimetre), from the surface down- 
wards must contain these 2^ milligrammes ; which would 
give a total quantity of 25,000 milligrammes ( = 25 
grammes = 386 grains) to the square decimetre, calculated 
to a depth of 10 inches ; or 25,000 kilo. (24|- tons), to the 
hectare (2-J acres), i. e., somewhat more than ^ per cent, of 
the whole soil. 

A hectare which, from the surface downwards, contains 
no more than 250 kilo. r:= 550 lbs. of mineral matter (of 
which 50 kilo. = 110 lbs. are potash, and 25 kilo. = 55 lbs. 
are phosphoric acid) would, according to this calculation, 
be completely unsuitable for wheat ; for even though each 
wheat plant possessed, instead of one hundred, one thou- 
sand roots, each of the thickness of a hyacinth root, it 
would nevertheless not be able to receive by these more 
than a tenth part of its wants from the soil. 

According to our assumption, which probably barely 
reaches the full amount really present, a hectare must con- 
tain, from the surface downwards, in order to yield an 
average crop of wheat, at least 5000 kilo. (= 11,000 lbs.) 
of potash and 2500 kilo. {= 5500 lbs.) phosphoric acid."^ 

* If the mineral food, so very small in proportion to the whole mass of 



92 THEORETICAL AND PRACTICAL AGRICULTURE. 

If an average wTieat crop of 2000 kilo. {— 4400 lbs.) of 
grain and 5000 kilo, of straw, has removed one per cent, of 
the mineral food from the soil, the latter remains still pro- 
ductive for new wheat crops in the following years ; but the 
amount of produce diminishes. 

If the soil has by mechanical means been most carefully 
mixed, the wheat plants of the second year on the same 
field will find at each spot one per cent, less food, and the 
produce in corn and straw must in the same proportion be 
smaller. Under similar conditions of weather, tempera- 
ture, and fall of rain, only 1980 kilo. (= 4356 lbs.) of 
grain, and 4950 kilo. (= 10,890 lbs.) of straw, will be 
reaped in the second year ; and in each following year the 
crop must fall off in a fixed ratio. 

If the crop of wheat removed in the first year 250 kilo. 
(— 550 lbs.) of mineral constituents, and a hectare (2^ acres) 
of soil to the depth of 12 inches, contained one hundred 
times this quantity (25,000 kilo., or 24^ tons), there will re- 
main in the soil at the end of thirty years of cultivation, 
18,492 kilo. (= 18 tons) of food. 

Whatever then may have been the variations in the 
amount of produce from this field, in the intervening years 
caused by different conditions of weather, it is evident, that 
if there has been no replacement of the mineral matters re- 
moved, there can be obtained in the thirty-first year, under 
the most favourable circumstances, only iff = 0*74, or some- 
what less than J of an average crop. 

soil (2 grains in a cubic inch), were present in chemical combination with it, 
it is impossible to form an idea how it could be distributed in this state every- 
where in the soil, so as to be reached by the roots. The comportment of 
soils of the most different kinds towards solutions of these elements, shows 
that they are present and fixed in a way somewhat similar to colouring mat- 
ter in dyed stuffs, or in charcoal which has been used to decolorise a fluid ; 
in these cases a very small quantity in weight is sufficient to cover an extrac 
ordinary extent of surface. 



THEOKETICAL AND PRACTICAL AGRICULTURE. 93 

If these f of an average crop do not yield to the agri- 
culturist a sufficient excess of income over expenditure, if 
they merely cover his expenses, then the crop is no longer 
remunerative. He considers the field to be now exhausted 
for wheat crops, although it still contains seventy-four times 
more food than an average crop yearly requires. The 
effect of the total quantity of mineral food in the soil has 
been, that in the first year each root found in those portions 
of the soil with which it came in contact, the requisite 
quantity of these substances for its complete development ; 
and the result of the subsequent continuous crops has been, 
that in the thirty -first year only f of this quantity is found 
in these portions. 

A field exhausted for wheat cultivation, will produce 
remunerative crops of rye. 

An average crop of rye (= 1600 kilo., or 8520 lbs. of 
grain, and 3800 kilo., or 8360 lbs. of straw) extracts from 
the ground per hectare only 180 kilo. (= 396 lbs.) of 
mineral matter. Under similar circumstances, one rye 
plant takes up only 180 milligrammes (= 2 "77 grains). 

If a soil must contain 25,000 kilo, of mineral matter, in 
order to produce an average crop of wheat, a soil in which 
there are only 18,000 kilo, of the same substances, is rich 
enough for an average crop of rye, and will yield a number 
of such crops which shall be remunerative. 

According to our calculation a field which is exhausted 
for the cultivation of wheat, still contains 18,492 kilo, of 
mineral matter, which in their properties are identical with 
those required for rye. 

If we now inquire after how many years of continuous 
rye cultivation will the average crop fall to one of f the 
amount, we find, — assuming that this amount is no longer 
remunerative, — that after 28 remunerative crops, the field 
will be exhausted for the cultivation of rye. The mineral 



94 THEOKETICAL AND PRACTICAL AGRICULTURE. 

matters still remaining in the ground amount, however, to 
13,869 kilo. (= 13i tons.) 

A field on which rye can no longer be cultivated with 
profit, is not necessarily unsuitable for oats. 

An average crop of oats (2000 kilo, of grain and 3000 
kilo, of straw per hectare), withdraws from the soil 310 
kilo. (= 682 lbs.) of mineral matter, being 60 kilo. (= 132 
lbs.) more than a wheat crop, and 130 kilo. {— 286 lbs.) 
more than a rye crop. 

If the absorbent root surface of the oats were the same as 
that of rye, then oats following rye would not be a remu- 
nerative crop ; for a soil which furnishes 310 kilo, out of a 
stock of 13,869 kilo, for a crop of oats, loses thereby 2-23 
per cent, of its amount of mineral constituents ; whilst by 
our calculation the roots of the rye extract only one per 
cent. This can only happen if the root surface of the oats 
exceeds that of the rye 2-23 times. 

According to the above, the oat crops will exhaust the 
soil most rapidly. After 121 years the return of produce 
must sink to I of its original amount. 

None of all the causes which may diminish or increase 
the amount of a crop, has any influence on this law of 
exhaustion of the soil by cultivation. When the sum of 
the food has reached a certain point of diminution, then 
the soil ceases to be productive, in an agricultural sense, for 
a cultivated plant. If by incorporating with it atmospheric 
food, organic materials and salts of ammonia, the produce 
has been augmented for a number of years, the state of 
exhaustion will then occur sooner. On the other hand, 
any obstacle to the free absorption of food diminishes the 
amount of produce, and the limits of exhaustion are conse- 
quently reached at a later period. 

For each cultivated plant, there exists a similar law. 

This state of exhaustion inevitably happens, even when there 



THEORETICAL AND PRACTICAL AGRICULTURE. 95 

has been withdrawn from the soil by a course of crops only one 
of all the different mineral substances necessary for the nourish- 
ment of plants ; for the one which is awaniing, or exists in 
deficient quantity, renders all the others inefficient^ or deprives 
them of their activity. 

With each crop, each plant, or portion of a plant, taken 
away from a field, the soil loses a portion of the conditions 
of its fertility ; that is, it loses the power of again producing 
this crop, plant, or portion of a plant, after the expiration 
of a number of years of cultivation. A thousand grains of 
corn require from the soil a thousand times as much phos- 
phoric acid as one grain ; and a thousand straws a thousand 
times as much silicic acid as one straw ; if, therefore, 'there 
is a deficiency of a thousandth part of the phosphoric or 
silicic acid in the soil, then the thousandth grain and straw 
will not be formed. A single corn straw removed from a 
corn field, makes this field bear one corn straw less. 

If it is true that the mineral constituents of the culmi- 
ferous plants are indispensable for their growth, and must 
be supplied by the soil, if the plants are to flourish ; if it is 
true that among these mineral matters, potash, phosphoric 
acid, and silicic acid, are not conveyed to the roots in a state 
of solution, then it necessarily follows that a hectare ( 2^ 
acres), containing 25,000 kilo. (= 24^ tons) of the constitu- 
ents of the ashes of wheat, uniformly distributed through 
it, and in a state quite fit for assimilation by the roots, can 
to a certain point yield a series of remunerative crops of 
different species of straw plants, without any replacement 
of the minerals removed in the grain and straw, if a uniform 
state of mixture of the soil has been maintained by careful 
ploughing and other suitable means. The succession of 
such crops is determined by this, viz. that the plant culti- 
vated the second year shall take away from the soil less 
than that of the first ; or that it contains a greater number 



96 THEORETICAL AND PRACTICAL AGRICULTURE. 

of roots, or, in general, a greater absorbent root surface 
than the first. From the average crop of the first year, 
there would be a diminution of produce from year to year. 

The agriculturist, to whom uniform average crops are 
exceptions, and varying returns caused by changing states 
of weather is the rule, would most probably not have noticed 
this constant diminution, not even though his field had in 
reality possessed such favourable chemical and physical 
conditions as to have enabled him to cultivate on it for 
seventy years successive crops of wheat, rye, and oats, 
without replacing any of the mineral matters withdrawn 
from it. 

In* favourable years, good crops approaching nearly to 
an average one, would have alternated with bad crops in 
other years, but the proportion of unfavourable to favour- 
able crops would have constantly increased. 

The greater number of European fields under cultivation 
does not possess the physical character which has been 
assumed in the case just under consideration. 

In most fields all the phosphoric acid necessary for plants 
is not distributed in the state in which it is readily avail- 
able to the roots. One portion is simply dispersed through- 
out it in the form of little granules of apatite only (phosphate 
of lime), so that even though the soil may altogether con- 
tain more than a sufficient proportion, yet in its various 
portions there may exist in some too much, in others too 
little, for the wants of plants. The mechanical preparation 
of the soil would displace these granules, but would not 
cause their thorough distribution and incorporation with 
it. To effect this requires the co-operation of a chemical 
action. 

After each rye or oat crop there remains in the soil a 
considerable quantity of roots, which after one or two years 
entirely disappear. We know that these organic matters 



THEOKETICAL AND PRACTICAL AGRICULTURE. 97 

have undergone decay ; tliat tlieir constituents liave united 
with oxygen; and that the carbon has formed carbonic 
acid, which has accumulated in the air contained in the 
porous soil, as analysis shows us. 

When rain falls on this soil, it dissolves the carbonic 
acid, which thereby acquires the power of taking up phos- 
phate of lime. This carbonic acid water does not withdraw 
from the soil the phosphate of lime contained in it, but 
wherever it meets with the granules of apatite or phospho- 
rite, it dissolves a certain portion ; for in these granules 
there exists no cause of resistance to the action of the water; 
and except the cohesion between its own particles, no other 
extraneous influence prevents its solubility in water. 

Under these circumstances, a solution of phosphate of 
lime must consequently be formed, which spreads in all 
directions around each granule. Wherever this solution 
comes in contact with soil not already saturated with phos- 
phate of lime, the soil will take up and retain a certain 
portion of this salt. The portion of soil now saturated with 
phosphate will oppose no further obstacle to the wider dif- 
fasion of the solution. 

The same process is found to take place in the diffusion 
of the silicic acid and potash in the soil, when the latter 
contains silicates which can be decomposed by carbonic 
acid. There is then formed around each particle of silicate 
a solution of silicate of potash, the constituents of which 
are always again fixed, in the first place by the nearest 
lying, and then by the more remote portions of the soil. 

A certain time is required for the distribution through- 
out the soil of the food in the manner above described. 

If we suppose that our field had contained 25,000 kilo. 
of the ash-constituents of wheat, distributed in the most 
uniform manner through it; and in addition to this, but 
unequally distributed^ five, ten, or more thousand pounds of 

5 



98 THEORETICAL AND PRACTICAL AGRICULTURE. 

the same food, the phosphoric acid as apatite^ the silicic acid 
and potash as easily decomposed silicates; — if we further 
suppose that every two years a certain quantity of the last- 
named substances had been rendered soluble, and capable 
of distribution in the soil in the manner above mentioned, 
and in such proportions that the roots should have found 
everywhere in the soil these elements of food in the same 
proportions as in preceding years of cultivation — a suffi- 
cient amount, therefore, for a full average crop; then 
should we, under these circumstances, have obtained during 
a series of years full average crops, if we had interposed a 
year of fallow between each year of cultivation. Instead of 
thirty constantly-diminishing crops, we should in this case 
have obtained, during a period of sixty years, ihirXy full 
average crops, if the additional portion of minerals in the 
soil had proved sufficient during that time to replace every- 
where the phosphoric and silicic acids, and the potash, 
removed annually by the crops. With the exhaustion of 
the additional proportion of minerals in our field, the period 
of diminishing crops would commence ; and the further 
interposition from this time of fallow years would not then 
exercise the slightest influence on the increase of produce. 

In the case under consideration, had the supposed addi- 
tional quantity of phosphoric and silicic acids, and potash, 
not been unequally but uniformly distributed throughout 
the field, and everywhere completely accessible to the roots of 
plants, and in a state fit for absorption, then thirty full cro"^^ 
would have been reaped in thirty successive years, without 
the interposition of a year of fallow. 

Let us return to our field, in which we assumed that 
there were 25,000 kilo, of ash-constituents of wheat, tho- 
roughly dispersed throughout it, and in a state fit for 
absorption, and that it was sown each year with wheat; 
let us now suppose that in each crop the ears only were 



THEORETICAL AND PRACTICAL AGRICULTURE. 99 

cut from the straw, and tliat the entire straw was left on 
the field and imediatelj ploughed in ; then must the loss 
of minerals be less in this year than before, for all the con- 
stituents of the straw and the leaves have remained in the 
ground ; we have only removed from the field the mineral 
constituents of the grain. 

Among the substances which the straw and leaves have 
obtained from the soil, are found all the constituents of the 
seed^ but only in altered proportions. If we express by the 
number 3, the whole phosphoric acid removed by the grain 
and straw together, the loss would be represented by the 
number 2, if the straw remains in the ground. The decrease 
of produce in a field in a succeeding year bears always a 
definite proportion to the loss of mineral substances by the 
preceding crop. The following crop of grain will be a 
little larger than it would have been, had the straw not 
been left in the ground. The produce of straw will be 
nearly the same as in the preceding year, for the conditions 
for the formation of straw have been but slightly altered. 

By thus taking less from the field than formerly, we 
thereby increase the number of remunerative crops, or in 
other words, the total amount of grain produced in the 
whole series of corn crops. A portion of the straw-consti- 
tuents is converted into corn-constituents, and in this form 
is now removed from the soil. The period of exhaustion 
will always come, but under these circumstances it occurs 
at a later date. The conditions for the production of grain 
go on constantly decreasing, for the minerals removed by 
it have not been replaced. 

This relation would still have remained the same, had 
the cut straw been carted about the field, or been ploughed 
in after serving for litter to cattle. What has been sup- 
plied to the field in this way, had been originally taken 
from it and cannot therefore enrich it. When we reflect 



100 THEORETICAL AND PRACTICAL AGRICULTURE. 

tliat the combustible elements of straw are not furnislied 
bj the ground, it is clear that in leaving the straw in the 
ground, we really leave only the constituents of its ash. 
The field was thereby enabled to yield a little more than 
it otherwise would have done, simply because less had been 
taken from it. 

Had we also along with the straw ploughed in the grain 
or its ash-constituents ; or instead of the wheat grain re- 
turned to the field a corresponding quantity of another 
seed, rape-dust (that is, rape-seed freed from its fatty oil), 
which contains the same ash-constituents, the composition 
of the soil would have remained the same as before, and the 
same amount of produce would have been obtained as in the 
preceding year. 

If after each crop, the straw is always returned in this 
manner to the field, the further result then is, an inequality 
in the composition of the active constituents of the soil. 

We have assumed that our field contained the mineral 
matters of the whole wheat plant in the right proportions 
for the formation of straw, leaves and grain. By leaving 
the straw-constituents in the soil, whilst those of the grain 
were constantly removed, an increase of the former took 
place, when compared with the proportion of grain-consti- 
tuents still remaining in the field. The field retained its 
productiveness for straw, but the conditions for the forma- 
tion of grain decreased. 

The consequence of this inequality is an unequal deve- 
lopment of the whole plant. So long as the soil contained 
and supplied, in the proper proportions, all the necessary 
mineral matters for the uniform growth of all parts of the 
plant, the quality of the seed and the proportion between 
straw and grain in the diminishing crops remained uniform 
and unaltered. But in proportion as the conditions for the 
formation of straw and leaves became more favourable, so 



THEORETICAL AND PRACTICAL AGRICULTURE. 101 

did the quality of the seed deteriorate as its quantity dimi- 
nish. The sign of this inequaUty in the composition of 
the soil, as a consequence of cultivation, is the diminution 
in weight of the bushel of corn. Whilst at first a certain 
portion of the constituents of the returned straw (phospho- 
ric acid, potash, magnesia) was expended in the formation 
of grain, at a later period the reverse of this takes place, 
and demands are then made on the grain-constituents 
(phosphoric acid, potash, magnesia) for the formation of 
straw. We may imagine that when there exists in a field, 
this inequality in the conditions for the formation of grain 
and straw, a culmiferous plant may, under conditions of 
temperature and weather favourable for the production of 
leaves, yield an enormous crop of straw with empty ears. 

Vine-dressers and gardeners prune trees and vines in 
order to obtain larger fruit and in greater quantity, by 
thus limiting the formation of twigs and leaves ; and in 
many districts, as in lower Bavaria, it is often considered 
advantageous to cut down or feed off the corn when half 
grown. It is found that by this proceeding a larger amount 
and a better quality of grain are obtained. In tropical 
regions many culmiferous plants bear no seed, or but a 
small quantity, because the soil does not contain the 
proper proportion of conditions for the formation of seed 
and leaf. 

The size of the seed in many plants, is in inverse pro- 
portion to the development of the leaf. Tobacco, poppy, 
and clover have proportionably smaller seeds than the 
culmiferous plants. 

The agriculturist can influence the direction of the vege- 
tative force only through the soil ; that is, through the 
proportion of the elements of food which he supplies to it. 
For the production of the largest crop of grain it is requisite 
that the soil contain a preponderating proportion of food neces- 



102 THEORETICAL AND PRACTICAL AGRICULTURE. 

sary for the formation of seeds. For turnips^ ^^(^fy and 
tuberous plants, this condition is reversed. 

An average crop of turnips with leaves contains five 
times, a clover or potato crop twice, as much potash as the 
grain and straw of a wheat crop from an equal surface. A 
clover and a potato crop together remove from two fields 
of a hectare each, as much phosphoric acid as the grain of 
three wheat crops from three fields of the same size. 

It is therefore evident, if we cultivate potatoes and 
clover on our field which contains 25,000 kilo, of the mine- 
ral constituents of wheat, and remove the whole produce 
of tubers and clover, that we withdraw from the soil of 
these two fields as much phosphoric acid, and three times 
as much potash, as bj three wheat crops. It is certain, 
that this removal from the soil, by another plant, of these 
important mineral substances, produces a great effect on its 
fertility for wheat ; the yield and the number of the wheat 
crops diminish. 

If, on the other hand, during a period of two years, we 
had cultivated on the field, wheat in the first year, and 
potatoes in the second, and had ploughed in the whole of 
the potato crop and the wheat straw, and had continued to 
do this for sixty years, we should not by these means have 
in the least degree altered or augmented the produce in 
grain, which the field was capable of yielding. The field 
has neither acquired nor lost anything by the cultivation of 
potatoes, for these were always left in the field. When the 
grain crops taken from the field have diminished the store 
of mineral matters to I of their original quantity, then this 
field ceases to furnish a remunerative crop, if 3 of an 
average return no longer yield any profit to the agricultu- 
rist. We arrive at the same results, if, instead of potatoes, 
we had interposed crops of clover, and had in the same 
way each year ploughed it in. We have assumed that the 



THEORETICAL AND PRACTICAL AGRICULTURE. 108 

physical condition of the soil was most favourable, and 
consequently, could not be improved by incorporating with 
it the organic matters of the clover and potatoes. Even 
had we removed the potatoes from the field, mown and 
dried the clover, and then carted the potatoes and hay back 
to the field, or made them first pass through the cattle 
stalls, or made any other use of them ; had we in this way 
returned to the field the whole sum of mineral matters in 
both crops, we should not by all these operations have pro- 
duced from it in thirty, sixty, or seventy years, a single 
grain more than would have been obtained without all these 
changes. During this whole period the conditions for the 
production of grain have not increased, but the cause of 
decrease in the crops has remained the same. 

The ploughing in of the potatoes and clover could pro- 
duce a beneficial effect only on those fields, in which a 
favourable physical state did not exist; or in which the 
mineral matter was unequally distributed, and was partly 
inaccessible to the roots of plants. But an action of this 
kind is just the same as that of green manuring, or of one 
or more years of fallow. 

By the incorporation with the soil of the clover and 
organic substances, the amount of decaying matters and of 
nitrogen in it is increased from year to year. All that these 
plants received from the atmosphere remained in the 
ground, but the enriching of the soil with these otherwise 
useful matters cannot effect the production of more grain 
than formerly ; for this depends on the proportion of the 
minerals in the soil, and these have not been increased, but 
on the contrary, have constantly decreased, in consequence 
of the removal of the corn. By the increase of nitrogen, 
and of decaying organic matter in the soil, the produce 
might possibly be augmented for a number of years, but 
the period at which such land would no longer produce a 



104 THEORETICAL AND PRACTICAL AGRICULTURE. 

remunerative crop, occurs in sucli circumstances only so 
much the more quickly. 

If we cultivate on three different wheat fields respec- 
tively, wheat, potatoes, and clover, and plough all the 
potatoes and clover yielded by the other two into the 
wheat field, from which the grain alone is removed, we 
shall by these means render the latter more fertile than 
before, for we have enriched it by the whole amount of 
minerals which the potatoes and clover had extracted from 
the other two fields. It has received three times as much 
phosphoric acid, and twenty times as much potash, as the 
grain has carried away. 

This wheat field will now be able to produce in three 
successive years, three full grain crops ; for the conditions 
for the production of straw have remained unchanged, 
whilst those for corn have been increased threefold. If 
the agriculturist in this manner raises in three years as 
much corn as he would have done in five on the same fields, 
without the co-operation of the mineral constituents of the 
clover and potatoes, then has his profit now evidently become 
greater^ for he has reaped with the seed for three crops as 
much as he would have done in the other case, with the 
seed for five. But the other two fields have lost in fertility 
as much as the wheat field has gained ; and the final result 
is, that with less cost of cultivation^ and ivith more profit than 
before, the agriculturist has in his three fields anticipated 
the period of exhaustion which would inevitably have over- 
taken them by the continued withdrawal in grain of the 
mineral constituents of the soil. 

The last case that we have to consider is, when the agri- 
culturist, instead of potatoes and clover, cultivates turnips 
and lucerne, which, by means of their long and deep pene- 
trating roots, extract a large quantity of mineral matter 
from the subsoil, which is not reached by the greater num- 



THEORETICAL AND PRACTICAL AGRICULTURE. 105 

ber of the roots of tlie cereals. Where the fields possess a 
subsoil, favourable to the growth of these plants, we double, 
as it were, the extent of surface capable of cultivation. If 
the roots of these plants received half of their mineral 
matters from the subsoil, and the other half from the arable 
soil, the latter will lose by the crops only half so much as 
they would have done, had the whole of the mineral food 
for these crops been obtained from the arable soil alone. 

The subsoil considered in the light of a field apart from 
the arable soil, thus furnishes to the turnip and lucerne 
crops, a certain quantity of mineral matter. If we sup- 
pose that in harvest the whole of the turnip and lucerne 
crops had been ploughed under in the wheat-field, which 
had yielded an average crop of grain, and in this way as 
much and more mineral matter had been returned than the 
grain had removed ; then by these means, this wheat-field 
can he maintained at the same degree of fertility at the expense 
of the subsoil^ just so long as the latter continues productive for 
turnips and lucerne. 

But since turnips and lucerne require for their growth a 
very large quantity of mineral matter, the subsoil will be 
the sooner exhausted, in proportion to the smaller quantity 
of these substances it contains. Now as the subsoil is not 
in reality separated from the arable soil, but lies beneath it, 
it can scarcely receive back any of the substances it has lost, 
because the arable soil retains that portion of them which 
has been added to it. It is only that part of the potash, 
ammonia, phosphoric, and silicic acids, which has not been 
taken up and fixed by the surface soil that can penetrate 
to the subsoil. 

By the cultivation of these deep-rooting plants, super- 
abundance of food can consequently be obtained for all 
those which derive their nourishment chiefly from the sur- 
face soil. This supply will not, however, be of any dura- 

5* 



106 THEORETICAL JlND PRACTICAL AGRICULTURE. 

tion ; for, in a comparatively short time, many fields will 
cease to produce these plants, because the subsoil is ex- 
hausted, and its fertility is only restored with difficult}^ 
In the first place, lucerne no longer grows, and turnips are 
only now produced in so far as they are able to obtain theii 
full supply of minerals from the surface soil. Potatoes, 
which derive their supplies from the upper layers of the 
surface soil, endure the longest. 

The quantity of food which a plant receives from the 
ground is not alone dependent on the quantity which is 
present in the finest particles of the surface soil, but also 
on the number of organs which extract this food from the 
ground. Two roots will obtain twice as much as one. 

The crop is partly dependent on the first root forma- 
tion. 

A grain of wheat or barley contains within itself so large 
a quantity of food, that it stands in no need of the soil in 
the first period of its growth. The seeds of these plants 
when simply moistened, produce ten or more rootlets from 
six to eight lines in length. The heavier the grain, the 
stronger and more vigorous is the formation of roots. The 
seed corn, without receiving anything from the ground, 
extends in all directions its organs of absorption, by which 
it procures its food from a comparatively great distance. 
Hence the agriculturist attaches great importance to the 
careful selection of seed. 

Small seeds, such as those of tobacco, poppy, and clover, 
require a richer or more thoroughly prepared surface soil, 
to prevent the loss of a large proportion ; because the soil 
in the immediate neighbourhood of the seed must at once 
supply it with food after germination. Hence, as the agri- 
culturists say, such plants are more difficult to raise. 

The seeds of the cereals may be compared to a hen's 
egg, which contains within itself all the necessary elements 



THEORETICAL AND PRACTICAL AGRICULTURE. 107 

for the development of the young animal. Husbandry 
would certainly assume quite another form, if for every 
single cereal plant, as many seeds should be lost as is the 
case with poppies, tobacco, and even clover. 

The quantity of food wliich a plant obtains from one and 
the same soil is in proportion to its absorbent root surface. Of 
two species of plants^ which require the same quxintity and a 
similar relation of mineral food^ the one with double extent of 
root surface takes up double the quantity of food. 

If it is true that the constituents of the ash of plants are 
indispensable to their life and growth, it is evident that 
whatever else may exert a favourable influence on their 
growth, must be subordinate to the law^ that the soil, in 
order to be fertile in an agricultural sense for a cultivated 
plant, must contain the constituents of the ash in sufficient 
quantity, and in a state the most suitable for absorption. 

The agriculturist has to do with the soil alone ; it is only 
through it that he is able to exercise an immediate influ- 
ence on plants. The attainment of all his objects in the 
most complete and profitable manner, pre-supposes the 
exact knowledge of the effective chemical conditions for 
the life of plants in the soil ; it further pre-supposes, perfect 
acquaintance with the food of plants, and the source from 
which it is derived, as well as with the means for rendering 
the soil suitable for their nutrition, combined with experi- 
ence and skill in employing them in the proper way, and 
at the right time. 

It is evident from the above statement that the cultiva- 
tion of plants tends to drain or to render a fertile soil un- 
productive. In the produce of his fields destined for the 
food of man and beasts, the agriculturist sends away that 
portion of the active ingredients of his soil which con- 
tributes to the growth of this very produce. The fertility 
of his fields continuously diminishes, whatever may be the 



108 THEORETICAL AND PRACTICAL AGRICULTURE. 

plants he cultivates or the rotation he adopts. The export 
of his produce is nothing else than a spoliation of his soil 
of the conditions for its reproduction. 

A field is not exhausted for corn, clover, tobacco, and 
turnips, so long as it still yields remunerative crops with- 
out requiring restx)ration of the minerals which are removed. 
It is exhausted from the moment that the hand of man is 
needed to restore to it the failing conditions of its fertility. 

The great majority of our cultivated fields are in this sense 
exhausted. 

The life of men, of animals, and of plants, is connected 
in the closest manner with the return of all the conditions 
which promote the vital process. The soil by its constitu- 
ents contributes to the life of plants ; its continuous fer- 
tility is inconceivable and impossible without the return of 
those conditions which have rendered it productive. 

The mightiest stream, which sets in motion thousands of 
mills and machines, fails, if the streams and brooks run dry 
which supply it with water ; and these streams and brooks 
in their turn dry up, if the myriads of little drops of which 
they consist do not return in the form of rain to those 
spots from which they have their source. 

A field which has lost its fertility by the successive cul- 
tivation of different plants, acquires by the application of 
farm-yard manure^ the power of producing a new series of 
crops of the same plants. 

But what is farm-yard ma?2wre,^and whence is its origin ? 
The land of the husbandman is the source of all this 
manure. Manure consists of the straw which has served 
for litter, of the remains of plants, and of the fluid and 
solid excrement of man and animals. The excrement is 
derived from the food. 

In the bread which a man daily receives, he consumes 
the ash-constituents of the seeds of the cereals whose flour 



THEORETICAL AND PRACTICAL AGRICULTURE. 109 

has served for the preparation of the bread ; in flesh, the 
ash-constituents of flesh. 

The flesh of herbivorous animals, as well as its ash-con- 
stituents are derived from plants. These ash constituents 
are identical with those of the seeds of leguminous plants ; 
so that if a whole animal were burnt, the residual ash 
would not differ from that of beans, peas, and lentils. 

In bread and flesh, man consequently consumes the 
mineral matters of seeds, or of the constituents of seeds, 
which the agriculturist obtains from his land in the form 
of flesh. 

But a very small fraction of the large amount of mineral 
substances received by man in his food during a lifetime re- 
mains in his body. The body of an adult does not increase 
in weight from day to day, it therefore follows, that all the 
constituents of his food have passed again completely out 
of his body. Chemical analysis demonstrates that the ash 
of bread and of flesh exists in his excrement very nearly in 
the same quantity as in his food. The comportment of the 
food in his body is just the same as if it had been burnt in 
a furnace. The urine contains the soluble, and the faeces 
the insoluble mineral matters; the bad smelling ingredi- 
ents are the smoke and soot of an incomplete combustion. 
With these are also mingled the undigested and indigesti- 
ble remains of food. 

The excrement of swine fed on potatoes contains the ash- 
constituents of potatoes; that of the horse, the mineral 
matters of hay and oats ; that of cattle, the ash of turnips, 
clover, &c., which have served for their food. Farm-yard 
manure consists of a mixture of all these excrements 
together. 

By farm-yard manure, the fertility of a field which has 
been exhausted by cultivation, is completely restored. This 
is a fact which the experience of thousands of years has 



110 THEORETICAL AND PRACTICAL AGRICULTURE. 

established. In farm-yard manure tlie field receives a cer- 
tain quantity of organic, that is, combustible matter, and the 
ash-constituents of the consumed food. We have now to 
consider what part was played by the organic and inorganic 
matter in this restoration of fertility. 

The most superficial examination of a cultivated field 
shows, that all the combustible matter of plants which are 
reaped from the field are derived /rom the air^ and not from 
the soil. 

If the carbon of only a portion of the vegetable matter in 
the crop were derived from the soil, it is perfectly clear, that 
if the latter contained at first a certain amount of this element 
before the harvest, this quantity must become smaller after 
each crop. A soil poor in organic matter would be less 
productive than one in which it is abundant. 

Observation, however, shows, that a field under continued 
cultivation does not in consequence become poorer in organic 
or combustible matter. The soil of a meadow, which during 
ten years has yielded a thousand cwt. of hay per hectare, is 
not, after this period, poorer, but richer in organic substances. 
A clover field, after a crop, retains in the roots remaining in 
the soil more organic matter, and more nitrogen than it 
originally possessed; but it has become unproductive for 
clover, and yields no longer a remunerative crop. 

A wheat or potato field is in like manner, after a crop, 
not poorer than before in organic matter. In general the soil 
is enriched hy cultivation with combustible constituents, but its 
fertility nevertheless steadily diminishes. After a number of 
consecutive remunerating crops of corn, turnips and clover, 
these plants are found to flourish no longer on the same soil. 

Since, then, the presence of decaying organic m,atter in a soil^ 
does not in the slightest degree retard or arrest its exhaustion by 
cultivation, it is impossible that an increase of these substances 
can restore the lost capacity for production 



THEORETICAL AND PRACTICAL AGRICULTURE. Ill 

111 fact by incorporating with the soil of a field com- 
pletely exhausted, boiled saw-dust, or salts of ammonia, or 
both together, we cannot restore to it the power of yielding 
a second or third time the same series of crops. If these 
substances improve the physical character of the soil, they 
will exercise a favourable influence on the produce; but 
after all, their action still consists in accelerating the exhaus- 
tion, and rendering it more complete. 

Farm-yard, manure, however, restores thoroughly the 
power of producing the same series of crops, a second, third, 
or a hundred times. It arrests fully, according to the 
quantity employed, the state of exhaustion ; its application 
may render a field more fertile ; in many cases more so than 
it has ever been. 

The restoration of fertility by farm-yard manure cannot 
have been caused by the presence of combustible matters 
(carbonaceous and nitrogenous substances). If these pro- 
duced any good effects, they were of a subordinate nature. 
The action of farm-yard manure depends most undoubtedly on 
the amount of the incombustible ash-constituents of plants in itj 
and is determined by these. 

In the farm-yard manure the field received back in fact a 
certain quantity of all the minerals which had been with- 
drawn by the crops. The decrease in its fertility stood in 
exact relation with the removal and the restoration of the 
fertility with the restitution of these mineral substances. 

The incombustible elements of cultivated plants do Dot 
of themselves return to the soil like the combustible in the 
atmospheric sea from which they are derived. By the hand 
of man alone are the conditions of the life of plants given 
back to the soil. By farm-yard manure, in which these con- 
ditions are fulfilled, the agriculturist, as if by a law of nature, 
restores to his field its lost powers of production. 

A rational practice maintains the circulation of aU the 



112 THEORETICAL AND PRACTICAL AGRICULTURE. 

conditions of life ; and empirical practice breaks the chain 
which binds man to his home, by robbing the soil of one 
condition after another of its fertility. Though the empiric 
knows that the soil is different to-day from what it was 
yesterday, he nevertheless believes that it will be to-morrow 
what it is to-day. Founding on the experience of yesi^rday^ 
he teaches that the fertile soil is inexhaustible ; but science, 
guided by laws^ shows that the productiveness even of the 
most fertile soil, has its end, and that the very soil which 
appears inexhaustible, is exhausted. Because nature was 
kind and gave abundantly to the father, the empiric thinks 
that the son may also take abundantly and without any 
care for the future. On the fact that man has a home, and 
that the spot of earth, from which he toils with the sweat 
of his brow to gam his subsistence, is his home, depends the 
development of the human race. The continuance of his 
existence in his home is dependent on the law, that force is 
expended by use and maintained by supply. 



LETTER IX. 

Constant relation between the Sulphur and Nitrogen of Organic Compounds 
and the Alkaline Phosphates and Alkaline Earths of Cereals and Legu- 
minous plants — Mineral substances are as indispensable to the Life of 
Animals as to that of Plants — The amount of Phosphoric Acid and of 
Potash ascertained by analysis as existing in Soils is very small — The 
errors of Practical Teachers proved from the writings of Practical Agri- 
culturists — Fertility of land cannot be maintained by Nitrogenous and 
Carbonaceous Manures alone, but by the Restoration of the Ash Constitu- 
ents of Plants — Critical examination of the views o "Walz, a practical 
teacher, on the Nutrition of Plants — The mineral food of plants in arable 
soils is not inexhaustible — The volatile and organic matters of Manures 
are not the most important — The nature of Guano and its active con- 
stituents. 

The life and development of an organic being cannot be 
regarded as depending on chance. The assimilation of its 
food, the transformation of the elements of this food into 
living forms, and all organic processes, we find are go- 
verned by laws of necessity and reciprocal dependence, 
which, like the wheels of a machine, but in an infinitely 
more perfect manner, play into each other, and give rise to 
all its vital manifestations, its existence and continuation. 

Chemical analysis has shown that in the seeds of the 
cereals and of the leguminous plants, those sulphur and 
nitrogen constituents which, in the process of nutrition of 
men and animals, are employed in forming the combustible 
matters of blood, are always accompanied by alkaline phos- 
phates and alkaline earths, and that between both there ex- 
ists for each seed a fixed and unchangeable relation. When- 
ever the percentage of phosphoric acid increases or dimi- 



114 THEORETICAL AND PRACTICAL AGRICULTURE. 

nishes in any seed, we observe a like increase or diminution 
in the sanguigenous constituents. 

Chemical analysis has further shown that, in the blood 
of man who consumes bread, or in that of a warm-blooded 
animal fed on seeds, there exist the same incombustible 
matters as are contained in the food. The ash-constituents 
of the blood of cattle, sheep, swine, correspond to the 
ash-constituents of the turnips, herbs, or potatoes on which 
these animals have subsisted. 

The mineral elements of all the different parts of plants 
are, however, as indispensable to the life of animals, to the 
formation of their blood, and to its functions, as they are 
to the life of plants. 

Phosphoric acid is a constituent of the brain and of the 
nerves ; the alkaline phosphates and alkaline earths exist 
in the flesh of all animals : and a warm-blooded animal 
without bones (phosphate of lime), is inconceivable to us. 
The ash of green crops is rich in alkaline carbonates and 
common salt; and the blood of herbivorous animals 
abounds in alkaline carbonates, the chloride of sodium 
serving for the formation of the carbonate of soda of this 
fluid. Tea-leaves, of which man makes so much use in in- 
fusion, contain in their ash 17 per cent, of phosphoric acid ; 
in mulberry leaves, the food of the silkworm, the amount 
does not exceed 5 per cent. Each of these numbers has its 
physiological meaning. 

Were it possible for a plant to grow, flower, and bear 
seed without the co-operation of mineral matters, it would 
be utterly valueless to man and animals. A dog will die 
of hunger in presence of a dish full of raw or boiled white 
and yolk of eggs, in which is awanting one of the sub- 
stances most important for the formation of blood. The 
first trial teaches him that such food is as inefficient as a 
stone for the purposes of nutrition. 



THEORETICAL AND PRACTICAL AGRICULTURE. 115 

The constituents of the ashes of turnips and of meadow 
plants give them their nutritious value. Did they not exist 
in them, such plants would not be consumed by horses and 
cows. 

Everywhere in nature prevail those harmonious laws, 
which attach life to the earth, and maintain it in perpetual 
freshness and duration. Only there does the earth become 
old, and the germ of life is extinguished, where man in his 
narrow-mindedness ignores and denies their existence, when 
he opposes the circulation of the conditions of life, and de- 
ranges and obstructs their united action. 

It is certainly one of the most singular, if not one of the 
most inexplicable circumstances of the present day, that 
the existence of these natural laws is ignored by a great 
number of practical agriculturists, — precisely by those men 
who, in their occupation, are in a position to perceive 
daily the signs of their existence. Teachers of practical 
agriculture universally recognised to be the most distin- 
guished and skilfUl, have for sixteen years, and even up to 
a recent period, endeavoured to prove that these laws have 
no value in connection with fertile soils ; that the increase 
of the fertility of a field hy fallow and hy mechanical opera- 
tions^ and the removal of the mineral matters of the soil in the 
cwps, do not diminish the duration of this fertility : that the 
ground may retain continuously its fertility even when they 
neglect to supply the minerals which have been withdrawn^ 
that is, to restore the original composition of the soil. They 
teach that 2^ fertile field contains an inexhaustible amount of 
the ash-constituents of plants, and that, consequently, de- 
ficiency of these can never occur in it ; that the fertility of 
a soil is in exact proportion to the quantity of combustible 
matters^ of humus and nitrogen in it ; and that the want of 
fertility is owing to the want of nitrogen, and that the ex- 
haustion of the land depends up.on the withdrawal of the 



116 THEORETICAL AND PBACTICAL AGRICULTURE. 

latter. Manure, tliej assert, does not produce its beneficial 
effects by returning to the ground those elements which 
have been withdrawn from it in corn, clover, turnips, to- 
bacco, flax, hemp, madder, wine, &c., but it acts by its com- 
bustible constituents, and its effect is in proportion to the 
amount of nitrogen it contains. Its incombustible elements 
only quietly look on to see how the other matters are doing, 
something in the same way as the moon does when the dew 
is falling. 

The practical man regards with a smile of contempt the 
scientific proofs of his errors, but this smile does not arise 
from the feeling of conscious superiority which knowledge 
imparts, but it has its origin in a different source. 

Chemical analysis has with its rigorous methods proved, 
that of thousands of fields there is scarcely one which con- 
tains more than 1 per cent, of the ash-constituents of plants, 
of clover, for instance, in a state suitable to the wants of 
that plant. 

In 1848 the Royal Institute of Rural Economy in Berlin 
caused the soil from fourteen different places of the king- 
dom to be submitted to chemical analysis. The specimens 
were taken from fields which were as much alike as possi- 
ble, and a portion of each specimen handed to three different 
chemists for analysis. It resulted from these analyses that 
the mean quantity of phosphoric acid and potash (the latter 
in a state probably fit for assimilation) amounted, in five 
fields to t\ ; in six, to fV ^P to y\ ; and in three, to yV "^^P 
to y*V per cent. 

These analyses do not teach that a soil which contains y\ 
per cent, of these mineral substances is in consequence 
more fertile than another in which there exists only y^^ per 
cent. ; but they show with tolerable certainty that it con- 
tains a greater or less proportion of them. 

Practice, on the other hand, asserts that every soil con- 



THEORETICAL AND PRACTICAL AGRICULTURE. 117 

tains the ash-constituents of all plants in inexhaustible 
quantities. 

Chemical analysis points out in the most positive and 
undoubted manner, that a crop of clover removes from the 
soil in its ash-constituents a number of the conditions of 
its fertility for this plant ; it shows that, in the excrement 
of animals fed on clover, are contained the ash-constituents 
of clover, and that consequently, by the employment of 
such a manure, the whole of these ash-constituents which 
have been removed by the clover are again restored to the 
land. 

As harmonising with the scientific doctrine, that the 
exhaustion of a clover field really depends on the removal 
of the ash-constituenis of the clover, and the renewal of its 
fertility by farm-yard manure^ on the restoration of these 
same mineral matters, the writings of the most experienced 
agriculturists show, that a field which produced no clover^ 
can be made productive for a series of such crops by manur- 
ing with wood-ashes^ which contain the same mineral matters 
as clover ; that in the Netherlands this manure is of the 
most general application for this purpose; and that in 
Westphalia there is a proverb that "Ae pays double who 
buys no ashes.^^ (Schwerz, Anleitung zum prakt. Ackerbau, 
Bd. ii. S. 323.) It is a well-known fact that on strewing 
wood-ashes on a meadow, thousands of clover plants make 
their appearance where they were not visible before. 

Chemical analysis further shows that a similar relation 
exists between a soil and all plants which are grown upon 
it ; that a field which will no longer yield grain, but straw, 
bears a rich crop of the former if it has been manured with 
the ash-constituents of grain, and in many cases even with 
phosphate of lime alone. 

In complete opposition to the modern doctrine of our 
agriculturists, it is proved by indisputable facts that the fer- 



118 THEORETICAL AND PRACTICAL AGRICULTURE. 

tility of tlie soil is not increased by the amount of organic 
or combustible matters in it, or by the supply of these 
alone; that a soil which contains these in the greatest 
abundance is, as a rule, unproductive ; and that the appli- 
cation on a wheat field of nitrogenous matters — such as the 
salts of ammonia — in many cases diminishes rather than 
increases the crop of grain. It has further been proved 
that ammonia and nitrogenous manures do not augment 
the produce of clover, unless accompanied by the ash-con- 
stituents of the plant ; that by themselves they act favour- 
ably, only on such fields as are rich in mineral matters ; 
and that their continued use in such cases only more com- 
pletely exhausts the land — that is, makes it still more 
unproductive for future crops than it would have been 
without their action. 

""'If our fields really contained so large a quantity of the 
mineral matters of plants that they could not be exhausted 
by cultivation ; if the fertility was dependent on the pre- 
sence and their exhaustion on the absence of ammonia or 
nitrogenous substances, then an endless series of full crops 
should be obtained by the supply of these alone, without 
the addition of any mineral matter. It is, however, an 
established and indisputable fact, that the maintenance of 
the fertility of our fields is impossible without replacing the 
minerals withdrawn by the crops. Hence it follows that 
farm-yard manure does not act by its combustible elements, 
and that if the latter in any case produce a favourable effect, 
it is only when they are accompanied by the ash-constitu- 
ents of plants which have been removed by previous crops, 
and which are awanting in the field. 

I believe that among the readers of these letters there 
will scarcely be found one, at all acquainted with the rules 
of logic, who could have any doubts of the truth of the 
conclusions deduced from the chemical analysis of the soiJ^ 



THEORETICAL AND PRACTICAL AGRICULTURE. 119 

of plants, and of farm-yard manure. These analyses liave 
been made in thousands by different chemists in Germany, 
England, and France, and all agree perfectly in their results. 
If indeed the existence of a fact can be ascertained by the 
balance, there is none in the whole domain of chemistry 
more firmly established than this, that even the most fertile 
soil contains but an extraordinarily small quantity of the 
ash-constituents of plants in comparison with its chemically- 
inactive mass. It will be sufficient to give an idea of this 
fact when I state that the ablest chemists failed in discover- 
ing, before 1834, potash as a constituent of soils, of clay, 
and of limestones, because its amount is so small ; and that 
before the discovery of new and hitherto unknown re-agents, 
the simple detection in the soil of phosphoric acid (without 
any attempt to ascertain its quantity) was attended with 
the greatest difficulty. In these statements we find a justifi- 
cation of the views formerly held by philosophers that pot- 
ash, lime, and phosphoric acid are products of the vital pro- 
cesses or of the vital force. 

As is well known, there is an infinite variety in the com- 
position of the rocks and minerals, by the disintegration of 
which soil is formed. There are minerals which are rich, 
in potash, and which, like felspar, contain no lime ; in 
others, silicic acid or magnesia is awanting, or like lime- 
stones, they contain only traces of alkalies. It is only in 
exceptional cases, and in those rocks which are not exten- 
sively distributed, that it has been possible to estimate by- 
chemical analysis the weight of the phosphoric acid pre- 
sent. 

Like gold in the gold districts of America and of Australia, 
arable soil is the residual matter of rocks shattered by 
mighty mechanical actions, and decomposed by chemical 
causes. The granite gravel in the neighbourhood of Darm- 
stadt, in which can be detected felspar, mica, and quartz. 



120 THEORETICAL AND PRACTICAL AGRICULTURE. 

is as unproductive as pure quartz or pounded marble. A 
thousand years are perhaps necessary to form from many 
rocks, from basalt, granite, porphyry, trachyte, &c., a layer 
of arable soil, a line thick, such as is seen in wide valleys 
and low grounds, and to give it the physical and chemical 
properties which render it suitable for the growth of plants. 

Our modern teachers of agriculture inculcate that a fruit- 
ful soil is inexhaustible in the ash-constituents of plants, 
which are the essential conditions of their existence ; and 
the present system of agriculture is, in all its relations, 
based on this view, and on the further supposition that the 
increase of the produce of the ground can only be effected, 
or chiefly so, by the supply of organic matters, the ele- 
ments of which are obtained, not from the soil, but from 
the air. 

Practical agriculture asserts, that in such practical ques- 
tions which refer to soils^ crops, and manures, geology and 
chemistry have no voice ; experience alone can decide in 
such cases, and the deductions of science are not confirmed 
by it. 

We will now examine a little more narrowly the nature 
of this experience, and the grounds on which she bases her 
teaching. If founded in truth, it must secure the duration of 
the fertility of productive soils : it must provide practical 
agriculturists with the means of restoring to their land the 
fertility lost by cultivation. If those who follow such 
teaching are ever in want of these means, then is its con- 
demnation pronounced. 

Since the commencement of the contest regarding the 
scientific principles of agriculture, many excellent agricul- 
turists have communicated to me the most interesting 
proofs, from their own practice, of the truth of these prin- 
ciples, which they have hesitated to publish in an agricul- 
tural journal, through fear of being involved in a discus- 



THEORETICAL AND PRACTICAL AGRICULTURE. 121 

sion, whicli, as they very modestly expressed it, they had 
not sufficient scientific knowledge to carry on. In the po- 
sition which I occupy, I stand, as may be supposed, 
towards agriculturists who cultivate their own land, only in 
social relations of the most instructive and agreeable nature 
to myself; when, therefore, in these letters, I speak of 
practical agriculture, or practical agriculturists, as a matter 
of course only literary practical agriculturists are meant, 
and those who write and lecture in support of the doctrines 
of the school to which they belong. Among our agricul- 
turists are to be found many men of the greatest intelli- 
gence and information, who, like the gentleman, general, 
lawgiver, and consul of Home's best age, follow, from in- 
clination, agriculture as the noblest occupation, and manage 
their own estates, No one can reasonably expect that 
such men are to account for views and doctrines which 
are not theirs, but which they have adopted as they were 
taught. 

A totally different relation, however, exists between 
science and the writers on practical agriculture, whose com- 
petence to pronounce an opinion on the present important 
questions may not be disputed. From such men it must 
absolutely be required that they bring to the discussion of 
such questions, so much of the rudiments at least of che- 
mistry, physics, and geology, as are usually taught in 
ordinary schools, so that no doubts may be raised as to their 
intellectual capacity to comprehend correctly the questions 
at issue. 

The simple statement of the views and doctrines from his 
last work, of one of the ablest and most influential teachers 
of agriculture, as to the composition of the soil, the causes 
of its fertility and exhaustion, and the action of manures, 
will be sufficient to enable us to form an opinion on this 
point. This publication is expressly intended by the 

6 



122 THEORETICAL AND PRACTICAL AGRICULTURE. 

author to correct scientific teaching, aLcL to bring it into 
harmony with practical experience.* 

In the application of his theory to practice, the author 
of this publication puts forward as a fundamental principle 
that, " the soil (the surface and sub-soil included), may be 
said to contain an inexhaustible supply of those mineral 
elements of food which it received at first from nature, and 
furnishes by disintegration to plants." — (s. 116.) 

The following proposition is propounded by him, " Is 
the soil of a field of such a nature that it can be completely 
exhausted in a shorter or longer period of its soluble and 
insoluble mineral matter, if we do not restore to it the por- 
tion which is taken away by the crops ?" and it is answered 
in the following way : — (s. 28.) 

" The soil consists of disintegrated rocks, and either rests 
upon these same rocks or on others elsewhere ; the trans- 
ported soil may, nevertheless, have remained the same, 
and corresponds at least to the rocks from which it has its 
origin (p. 29, &c.). 

" All rocks undergo disintegration, and the products 
when not removed remain resting upon these rocks. The 
disintegration is chiefly effected by atmospheric causes, 
which extend their action down to the rocks lying deep 
under the debris. If, then, a soil is fertile for a given class 
of plants, and contains the mineral food for these plants in 
sufficient quantity, in proper proportions, and in a state fit 
for assimilation, and if it still rests upon the original rocks 
from which it was produced, then these underlying rocks also 
contain the same mineral food as the soil and subsoil, and in 
the same proportions. 

* " On the Nutrition of Agricultural Plants. An Examination, in an 
Agricultural Point of View, of the Fifty Axioms of Baron Liebig," by Gustav 
Walz, Director of the Agricultural Academy at Hohenheim, Stuttgart. Cotta, 
1857. 



THEORETICAL AND PRACTICAL AGRICULTURE. 123 

"If we withdraw from the soil its constituents by crops, 
its volume diminishes, and the rocks are thereby rendered 
more accessible to the action of the atmosphere. If the 
disintegration of the latter proceed in the same ratio as the 
constituents of the soil above them are withdrawn, then 
shall we be able to obtain crops from it without restoration 
of the mineral matters, until the whole quantity in the soil, 
and in the rocks, be consumed. 

" Suppose the soil of an hectare field (2-| acres), weighs 
4|- millions kilogrammes, and contains 10 per cent, of the 
mineral food of wheat plants in the right proportions and 
in a state fit for assimilation, such a field could, without 
any further supply, produce 1829 corn-crops. A three- 
crop rotation could last 2742 years without restoration of 
the mineral matters ; and were the rocks at the commence- 
ment of the tillage already disintegrated to the depth of 
several feet, as is generally the case^ then the three-crop 
rotation would have the prospect of enduring for each foot 
depth of earth other 2742 years. After this period, how- 
ever, the rocks under the subsoil will again undergo further 
disintegration, and thus there is a prospect of continuing 
tillage until the rocks forming the soil are entirely disin- 
tegrated, and the mineral constituents consumed. But 
there comes then another class of rocks under these, &c., &c. 

" By yearly removing ash-constituents from the soil, its 
volume is reduced. The agriculturist, however, preserves 
a soil of the same depth by turning up an equal quantity 
from the subsoil. If all the mineral food in the soil has 
been consumed, we have lost 10 per cent., and turned up 
10 per cent, from the subsoil. The turned up mass of 
earth, however, only contains 10 per cent, of mineral food. 
Hence, only yV of the withdrawn matters is replaced, the 
remaining y^o being waste matter. The second period of 
the supposed three-crop rotation would therefore not last 



124 THEOKETICAL AND PRACTICAL AGRICULTURE. 

2742 years, but only j\ of this time, viz., 274 years ; it is 
only after several such periods that the field would be ex- 
hausted. In the end there would remain nothing but insoluble 
silica and clay. To maintain the fertility of this soil in 
mineral matters, the withdrawn ash -constituents must again 
be supplied to the soil, or the waste matter lying on the 
subsoil be removed. In this operation nature helps us by 
yearly washing away the soil, in proportion to its greater 
or less inclined position. Finally, with respect to the re- 
placement of mineral matter in the soil, even rain, and 
wind also, assist in supplying them. 

" Thus, the restoration required, after a shorter or longer 
time, of the mineral matters removed by crops, in such a 
soil as we have supposed above, may take place only after 
thousands of years ; in a soil with 1 per cent, of mineral 
matters, after hundreds of years; and with j\ per cent., 
after tens of years. 

" The transported soil comports itself in a similar manner 
to the untransported ; the rocks lying under it will likewise 
undergo decomposition, &c., &c." 

Our teacher of practical agriculture concludes his argu- 
ment with these words : " The two axioms, viz., 

1st, " The increase of the fertility of a field by fal- 
low and mechanical operations, and the removal of 
the mineral substances in the crops without replacing 
them, are followed, after a longer or shorter period, by 
continued sterility;" and, 

2ndly, ''If the soil is to preserve permanently its 

fertility, the mineral matters withdrawn from it must, 

after a shorter or longer period, be replaced ; that is, 

the composition of the soil must be again restored," 

these two points apply, therefore, in our time, only to soils of 

the very worst description, which required fronn the very com- 

mencement a supply of these substances.'''' (W. S. 34.) 



THEORETICAL AND PRACTICAL AGRICULTURE. 125 

The above argument of one of our best teachers of prac- 
tical agriculture, which professes to harmonise with his 
agricultural experience, might well awake, in the minds of 
many of our reflecting agriculturists, just doubts as to the 
truth of the prevailing system of agricultural teaching. 

Sound common sense demands, in proof of the proposi- 
tion, that only the very ivorst kinds of soil require for the pro- 
duction of further crops ^ the restoration of the withdrawn 
mineral matters — that numerous instances should be adduced 
from common agricultural experience that a fertile soil, in 
order to continue productive, stands actually in no need of 
this supply of these matters ; that for ten, twenty, or a 
hundred years, it has annually yielded crops without any 
replacement whatever of the withdrawn minerals ! 

This proof, the only one which the writer from his point 
of view could adduce for refuting the results of the chemical 
analysis of soils, he still owes us, as well as the proper defi- 
nition of his notion of a "fruitful field." It is evident, 
that if the term "fruitful field" includes only those fields 
which exist as exceptional cases in Hungary, in many parts 
of Eussia, in low lands and valleys, and which are used as 
meadows, and appear to be inexhaustible because they are 
not yet exhausted, then the soil of ninety-nine oat of every 
hundred fields that are called fertile in Bavaria, Prussia, 
and Saxony, belongs to the worst kinds — a view, which no 
one can support. 

Our teacher of practical agriculture does not pay any 
attention to these actual facts, but brings forward his proofs 
in his own peculiar way. Without telling us what he 
understands by rocks, soil, and subsoil, and what kinds of 
rock, soil, and subsoil he means, he proceeds to apply these 
terms as if all soils, rocks, and subsoils were identical ; and 
leads us to believe that all soils, after their exhaustion by 
crops, leave, as a residue, quartz and clay. Such an asser- 



126 THEORETICAL AND PRACTICAL AGRICULTURE. 

tion, however, he would not seriously make, for in that 
case a great part of Wurtemberg would be w ithout any 
soil. 

To come to an agreement in a discussion, people must 
understand each other ; for if the one individual means by 
a word, sometimes one thing, and sometimes another, it fol- 
lows that the other cannot understand him ; for, in order 
to understand, we must have distinct ideas. A scientific 
definition is nothing but an ordinary one, only definite and 
unchangeable in its meaning. 

If an agriculturist speaks of his cattle which give him 
milk and manure, his neighbour agriculturist understands 
that he means his " cows." The production of milk and 
manure does not, however, constitute the scientific defini- 
tion of a "cow," for it does not exclude the idea which 
might be entertained by a third person that all animals 
which produce milk and manure are cows, or that a cow 
which gives only manure and no milk is not a cow. 

The same holds good in chemistry with the notion con- 
veyed by the word soil^ and also with regard to what is 
called experience; the word experience in an unscientific 
sense always recals to mind the man who was seized with 
sneezing when it thundered, and who always went out 
with his umbrella in the most beautiful weather, if he had 
happened to sneeze in the morning, because, according to his 
experience^ it was sure to be a thunder storm. 

In the argument of our teacher of agriculture, there is, 
in fact, " no soil " — that is, nothing which an agriculturist 
from experience knows as such; but it cannot be denied 
that the argument takes a wide range and view of things. 

The diminution of volume of the soil by the removal of 
mineral substances is evident ; amounting yearly, if my 
calculation does not mislead me, in the three-crop rotation 
to the 4V P^^t ^^ ^^® thickness of a spider's thread. 



THEORETICAL AND PRACTICAL AGRICULTURE. 127 

Equally clear and intelligible is the way in whicli nature 
is made to help plants, when the surface soil is exhausted, 
to obtain their nourishment from the sub-soil. The soil is 
in this respect made to comport itself to plants somewhat 
like a mixture of /^ of quartz and j\ of peas to a brood 
of fowls. When these birds have picked the peas from 
the soil, then comes the cock, like nature, afterwards, and 
scratches and scrapes away the useless matters. The saga- 
city of our teacher will of course also explain what becomes 
of those four million kilogrammes of waste matter which 
are yearly washed away in this manner from 1829 
hectares ; as well as show that the loss of mineral matters 
is of no importance to those neighbouring fields from which 
the wind and rain have carried them to our own. 

The experienced teacher of practical agriculture, in order 
to refute a deduction of exact science which he holds to be 
false, invents a case which does not exist in nature, and is 
simply impossible, or at least unknown ; and the conclu- 
sion to which he had previously carefully prepared his pre- 
mises to lead, he applies to actual cases. He imagines a 
fertile field extremely rich in the ash-constituents of plants, 
and supposes it to gain from below, in the most dexterous 
manner, what is taken from the surface ; and having in 
this way made it inexhaustible, he then draws the con- 
clusion that all fields which are fertile, must comport them- 
selves exactly like this imaginary field. It follows, then, 
as a matter of course, that the worst soils, under which can 
be understood only those which are absolutely sterile, must 
have required a supply of ash-constituents from the very 
beginning; for it is impossible to assume that, in the 
absence of all mineral food, which is taken for granted to 
be the case, they could have produced crops without these 
ash-constituents. It is therefore evident that if all fertile 
soils are inexhaustible in mineral matters, it is only the 



128 THEORETICAL AND PRACTICAL AGRICULTURE. 

unproductive which require a supply of these substances 
in order to become productive, and a renewal of the wasted 
portion in order to remain fertile. 

If an ignorant peasant, who has for thirty years seen 
crops follow the ploughing and sowing of his land, who 
knows that his father and grandfather had also reaped for 
thirty years from the same land after ploughing and sow- 
ing, believes himself entitled from these facts to conclude 
that this same land will still yield crops for thirty, sixty, a 
hundred years, or for an indefinite period, we must hold 
him excused on account of his ignorance. But when this 
peasant acknowledges that his grandfather, father, and he 
himself, have been obliged to manure this land each year, 
and then asserts that his field has never received ash- 
constituents in the manure, or that the ash -constituents it 
received have produced no effect upon the crops, and that 
their supply has consequently been of no advantage, we 
turn from him with pity. 

If the peasant had been capable of making a correct 
observation, he would probably have perceived that his 
manure heap constantly diminished in activity, and that 
his grandfather with very little manure obtained much 
larger corn crops than he now does with all his manure ; 
he would further have observed that he has now been 
obliged to include in his rotation plants which were not 
required by his grandfather, in order to maintain the pro- 
ductiveness of his fields for corn crops. 

We have believed that the object the agriculturist had in 
view was the production of grain and flesh, and that the 
thoughts of the guides and teachers of practical hus- 
bandry had been directed to ascertain the best means of 
maintaining the grain and pasture fields in a uniform 
condition of fertility. We are now taught better by the 
writings of our modern teachers of agriculture : the pro- 



THEORETICAL AND PRACTICAL AGRICULTURE. 129 

duction of flesh and grain is subordinate to that of fcrm- 
yard manure. 

For cereals, the soil, they tell us, is always fertile if there 
be only enough of manure. "Above all things let us have 
fodder enough ; the cereals will then follow of themselves." 
" Science does not teach agriculturists much when she tries 
to teach them to force nature," " when she tries to make 
them do without farm-yard manure." (W. S., 127.) "From 
the necessity for the rotation of crops agriculture does not 
wish to be emancipated, for farmers could even now free 
themselves partly from it if they could only manure more 
largely." (W. S., 129.) "Most agriculturists would un- 
doubtedly much rather never cultivate anything but wheat 
and rapes ; but this would never do, for the soil must have 
its farm-yard manure, and without a proper rotation farm- 
yard manure cannot be made." (W. S., 129.) " Farm-yard 
manure may be termed the raw material, which agricul- 
tural industry is to convert into marketable articles." (W. 
S., 124.) " A rich soil is consequently one which produces 
much manure, and a poor soil one which produces little. 
Hence, therefore, the division of plants into manure-econo- 
raising^ manure-exhausting^ and manure-enriching plants. 
Now, as clover and lucerne are the real manure-producing 
plants, and manure is the soul of agriculture, everything 
depends upon them." 

Our practical teachers have reduced, as we see, the most 
difficult of all trades, which manufactures its products with 
the most complicated of all machines — organised beings — 
and the pursuit of which is dependent on influences over 
which human power has no control, to a most simple fun- 
damental principle, intelligible to the most stupid peasant- 
boy, viz., \kiQ j^roduction of manure hy fodder plants. 

To what results then has this excellent teaching, this out- 
cry after manure, led? Clearly and distinctly mav the 

6* 



130 THEORETICAL AND PRACTICAL AGRICULTURE. 

present condition of our fields be recognised by tbe follow- 
ing entreaty and appeal to our sympathy and compassion : 

" Were science only to give us the means to enable us to cul- 
tivate these 'plants {clover^ lucerne^ esparsette) upon the same 
ground with uniform su€cess^ more frequently than is the case 
ivith our present system^ then indeed would the philosopher'' s 
stone he found for agriculture; for as to the conversion of these 
plants into the forms adapted to the wants of man, we would 
look to thaty (W. S., 127.) 

This, then, is the result of the doctrine of these wise, 
clear-sighted, and skilful men, who assert that fertile soils 
are inexhaustible in the mineral food of plants. 

To procure farm-yard manure, science is good enough ; 
they wish to learn nothing from it, but only to obtain a 
small piece of the philosopher's stone. Then these expe- 
rienced individuals, who are crammed full of so much in- 
formation in chemistry, geology, botany, &c., will procure 
us flesh and bread in abundance : this every simple peasant 
can do if we only give him manure. Hence, little " Japhet 
in search of his Father," the poor child called " Mineral 
Theory," was so ill-used and ridiculed, because he was of 
opinion that the big purse would at last be emptied, by 
always taking out money without putting any in. But who 
could have thought twenty years ago, when there* was 
plenty of manure, that it would ever occur to these obsti- 
nate and wilful fodder plants to produce no more manure, 
and no longer to spare and enrich the ground ? The soil is 
naturally not the cause of this ; for they teach that it is 
inexhaustible, and those who have still manure enough 
believe that the source from which it is derived will always 
flow. Truly, if this soil could cry out like a cow or a horse 
which was tormented to give the maximum quantity of milk 
or work with the smallest expenditure of fodder, the earth 
would become to these aorriculturists more intolerable than 



THEORETICAL AND PRACTICAL AGRICULTURE. 131 

Dante's infernal regions. Hence, the advantageous prose* 
cution of this system of modern agriculture is only possible 
on large estates, for the spoliation of a small one would 
soon come to an end. Instead of stealing the leather, if 
they had bred the calf, it would have grown to an ox, and 
then we should have been saved from the fear of going 
barefooted at last. 

But we need not yet despair : These wise, prudent, and 
experienced men have found out the means of putting an 
end to the deficiency of manure. These means, they tell 
us, consist simply in making use of fresh, instead of rotted 
farm-yard manure. If short-sighted, careless agriculturists, 
who do yet not follow this plan, would only put it in practice, 
many of the complaints about deficiency of manure would 
cease. 

" Notwithstanding the general outcry about want of manure, 
and all the trouble taken to increase vegetation ; notwith- 
standing the great cultivation of fodder plants to produce 
farm-yard manure, it is allowed, nevertheless, when made, 
to go to waste on the dung-hill. We may assume that in our 
system of farming, the manure is carted out on an average 
at most half-rotted. Before the manure arrives at this state, 
it loses 25 per cent, of its mass, consisting chiefly oi precious 
nitrogen ; I will here, however, estimate the loss to he equal in 
value to what is left. If all agriculturists would employ 
their manure as fresh as possible, so that at most no more 
than 5 per cent, be lost, the increase of our cultivated plants 
would amount to 20 per cent. ISTot only would this 20 per 
cent, of the whole food employed in increasing the crop be 
converted into vegetable matter, but by its means a further 
quantity would also be drawn from the air and the soil," 
(S. 131.) 

*' An increase of the production of fodder is, howevei, 
not required, so long as we do not wish to augment vegeta 



132 THEORETICAL AND PRACTICAL AGRICULTURE 

tion Still more. Hence, the 20 per cent, of dung capital, 
could be solely expended on the greater production of grain, 
which would thus become so much larger, in comparison 
with that of cattle, which remains the same. The supply 
of grain would consequently be greater, its price more 
moderate, and this would put itself more in equilibrium 
with the production of cattle: producers and consumers 
would be equally benefited. But greater advantages would 
also be attained ; for, instead of expending upon the growth 
of corn the 20 per cent, of manure saved, agriculturists 
could also diminish their cultivation of fodder by 20 per 
cent. The production of corn remaining the same, that of 
cattle would be decreased 20 per cent., and hence the latter 
would rise in price, whilst that of corn continues the same. 
Were the 20 per cent, of manure saved, chiefly devoted to 
the growth of corn, and to a smaller extent to that of fod- 
der, producers and consumers would derive benefit from 
this plan ; only on the part of the former it would be greater, 
and at how small a cost — all by means of the 20 per cent, of 
volatile matter which careless agricultmnsts lose hy the neglect of 
the manure on their dunghills^ (S. 132.) 

Had there been any doubt on the point, this proposition 
would incontestably prove that the modern teacher of 
practical agriculture puts not the slightest value on the 
mineral constituents of stable-dung, but ascribes its entire 
effect to the combustible matters it contains. With the 20 
per cent, of these matters, which fresh farm-yard manure 
loses by rotting, the practical man would make us believe 
that 20 per cent, more corn, clover, or flesh could be 
produced. 

Because, straw manure had accidentally improved the 
physical quality of his land, and consequently exerted a 
more favourable action than short rotted manure, he teaches, 
in opposition to thousands of well established facts, that 



THEORETICAL AND PRACTICAL AGRICULTURE. 183 

fresh manure must produce larger crops on all fields. He 
would make us believe, that when we simply take away 
the grain from our fields and plough in the straw, their fer- 
tility in each succeeding year must receive an additional 
increase equivalent in amount to what the straw loses, when 
it has been used as litter, and converted into manure ! 

Now, what is the cause of this great effect of fresh farm- 
yard manure, and its advantage over that which is well 
rotted? This, also, the man of practice tells us: ^^ In fresh 
manure there is more nitrogen than in old ; the latter^ on the 
other hand^ contains more ash constituents.^'' (W. S. 101.) 
Hence, fresh manure is more efficacious than old ! Chemi- 
cal analysis, indeed, proves, that rotted farm-yard manure 
contains more nitrogen than fresh^ but in such matters 
practice must decide ; and since, according to its teaching, 
the larger crops could only have been the result of the greater 
supply of nitrogen^ it follows that chemical analysis must 
be in error. 

But, after all, the additional 20 per cent, of manure 
which the land of our experienced teacher of practical 
agriculture obtains, appears to him far from sufficient, 
for he says : " Now, since straw and fodder, the materials 
for manure, are expensive, and manure must be had at 
almost any price, and the latter comes tolerably dear in 
consequence of the low price of cattle produce, agricultu- 
rists have naturally been seeking for a long time back for 
a substitute for manure. Such a substitute has been lately 
found in Guano." 

Now^ what is guano, and in what way is its employment 
advantageous to the agriculturist? 

Guano consists of the residue of the excrement of fish, 
that is, flesh eating birds, and contains essentially the ash 
constituents of the flesh of fish, together with a certain 
quantity of ammonia salts. 



134 THEORETICAL AND PRACTICAL AGRICULTURE. 

Comparison shows that the better sorts of guano contain 
the ash constituents of grain, together with a certain quan- 
tity of phosphate of lime, which forms an essential element 
of the ash of our meadow and pasture plants. The effect 
of guano on our corn fields is therefore palpable. We 
have for hundreds of years removed from them, by the 
cultivation of corn, the ash constituents of grain, and by 
rearing cattle, we have also taken away a large quantity 
of phosphate of lime (in their bones) without replacing any 
of these matters ; we have, however, left them the condi- 
tions for producing straw. 

The increase of the produce of grain, by manuring with 
guano, is the natural consequence of the restoration of the 
elements of grain, which we have been at so much pains to 
drag from our fields. The astonishment of the corn pro- 
ducer at the powerful effect of guano, after all, arises from 
the fact that he sees a few handfuls of this substance act- 
ing more efficaciously than a cart-load of stable-dung ; and 
because in looking at the smallness of the quantity of 
the guano, and comparing it with the large increase of grain, 
his ideas about manure are completely confounded. 

To our experienced teacher of practical agriculture, 
guano is, as a matter of course, only a means ybr producing 
manure. Guano, in an agricultural sense, is a "supple- 
mental manure," which we ought to use so long as the 
supply lasts, for the purpose of increasing our dung capital. 
(W.S. 137.) 

That the effect of guano depends on the volatile and 
combustible materials it contains, caijnot, of course, admit 
of a question ; let us hear what would be the result of its 
employment. 

" The general use of guano can only be attended with a 
result similar to that which would take place if the 20 
per cent, of manure hitherto lost from the dunghills were 



THEOKETICAL AND PRACTICAL AGRICULTURE. 135 

in future to be made use of." " Those agriculturists who 
still allow their manure to rot, hence clearly act foolishly 
in buying guano before they derive the fullest advantage 
from their own manure." (W. S. 136.) No value what- 
ever is put on the ash constituents of the guano. 

The ideas of our teacher of practical agriculture of the 
comportment of a soil under cultivation are not less 
peculiar. 

'''' Notwithstanding that plants are yearly reaped an equal 
quantity can, on an average, be continuously removed every 
year from the soil (for example, from an unmanured mea- 
dow). This is the natural production of tlte soil. The soil 
remains, and continues to remain at a fixed agricultural point 
of production. (S. 103.) 

" K during a period of one or more years the plants 
which grow upon a soil die, and decay, an accumulation 
of decaying and decomposing products will thus be gradu- 
ally formed in it. There is thus furnished a further source 
of both kinds of food, and the development of plants is con- 
sequently promoted." (S. lOi.) 

" By further new and increased crops more ash constitu- 
ents than formerly, as well as products of decay, will be 
removed from the soil." 

" After a series of years, and a corresponding number 
of crops, the ground sinks again to its original degree of 
fertility — its fixed point of production. It has again at- 
tained its original composition, and as nothing else has been 
changed, this alteration of the soil must be the probable cause 
ofit& increased and again diminished fertility. ''^ 

" Stable-manure consists of decaying vegetable and ani- 
mal matter, which also contains a certain quantity of ash 
constituents, hence the development of plants can be as 
well promoted by stable-mannre as by plants which decay 
upon the fields themselves.''^ 



186 THEORETICAL AND PRACTICAL AGRICULTURE. 

From these propositions which are given as agricultural 
principles, it would follow that our cultivated fields com- 
port themselves like unmanured meadows. Whether we 
cultivate grain, turnips, or clover, on one and the same 
field, we may fairly expect continuously, and without any 
application of manure, an average yearly crop of the same 
amount. This would be the natural production, or the 
agricultural fixed point of the soil ! 

If we leave meadow plants, corn, and clover, to die and 
decay on the field, manure accumulates in the soil and ren- 
ders it more fertile. We obtain larger crops, and withdraw 
hy these means more ash constitue7its than before^ in consequence 
of which the ground becomes poorer. 

Having followed this course for some years, the ground, 
robbed of its ash constituents, sinks back to its fixed point 
of production. It has again attained its original composi- 
tion (that is, it contains no more combustible matters than at 
firsi\ and since nothing further has been changed (as everything 
depends upon this), then this alteration of the soil — the dimi- 
nution and increase of combustible matters in if — must be the 
probable cause of its increased and again diminished fer- 
tility. 

The views cited above are those of a single man, but 
with few exceptions belong to the whole class of practical 
agriculturists. What the author teaches is not an invention 
of his own, but he retails what he has learned. I have 
reviewed these doctrines, not for the purpose of exercising 
indiscriminate criticism, but because, without holding up to 
view the opinions of practical men, my own peculiar doc- 
trines might appear to many in the present day incompre- 
hensible, and perhaps, at no distant date, vain and object- 



I need not add one word more ; the passages just cited 
give the key to the conflict which has been raised about 



THEORETICAL AND PRACTICAL AGRICULTURE. 137 

the recognition and application of scientific principles in 
practice ; that the latter do not enter into the circle of ideas 
of practical agriculturists will now be easily understood. 

Many agriculturists are of opinion that in this contest it 
is a question of words, not of principles, and that an 
understanding is possible. They think that if they allowed 
the action of mineral substances, then, injustice, the other 
party will acknowledge that of combustible substances, and 
thus the conflict would come to a happy termination. K 
the contest for the recognition of scientific principles had 
in fact no higher object than the admission into broth of 
onions previously forbidden, or the compromise that eggs 
may be opened at both ends, then they are right. 

They are right so long as they entertain the opinion that 
the best master brewer of the best Bavarian beer is the fit- 
test man for a chair of brewing.* I, for my part, do not 
believe that such a man should be recommended as the 
proper person for imparting the scientific principles of 
brewing, even though he had for twenty years conducted 
the most extensive business of this kind with skill and 
profit. 

* This sentence refers to the arrangement of many German agricultural 
institutions. They are in general endowed with a considerable extent of 
land, which is managed like other government lands. The produce of the 
soil finds its way into the public coffers. The school and the land are united 
with each other in the person of the Director, to whom is intrusted the cul- 
tivation of the ground and the superintendence of the instruction ; in the 
net proceeds of the farm he has commonly a share. There are men who are 
endowed with capabilities for both offices, but it usually happens that a good 
practical man is not the best instructor, and the latter is not generally an 
individual who sets much value on obtaining great profits fi-om the land. 



LETTEK X. 

The empirical agriculturist is a trader — The duties of the empirical and 
rational agriculturist — Views of Albrecht Block — Rotation of crops not un- 
important ; an underground crop is followed by a better cereal — Cropping 
of land without manure, and the removal of produce, cause exhaustion — 
The spoliation system of agriculture — Exhaustion of the lands in North 
America by this system — Exhaustion of the Minas Geraes fields — High 
farming is a more subtle system of spoliation of the soil — Mutual relation 
of clover, turnip, and corn crops ; and the results of removing from the 
lands the mineral constituents of these crops respectively — The German 
system of farming before the Thirty Years' War — The German three-field 
system of rotation — Introduction of clover cultivation into Germany — 
Opposition to its introduction — False teaching in connection with the value 
of manures. 

The empirical agriculturist is a trader who produces 
meat and corn ; without troubling his mind about collateral 
matters, he simply seeks to gain from his fields the largest 
possible crops, and he holds that system of cultivation as 
the best which will yield him the richest harvest in the 
cheapest way, and in the shortest time. And why should 
he not? The same system of husbandry which he pursues 
has been followed for centuries before his time, and he sim- 
ply practises the lessons taught him by those who preceded 
him in the farming of his land. As they never inquired 
what might ultimately become of the land, and what effect 
their system of cultivation might have upon it — why should 
he trouble his mind about it ? If he can succeed in making 
a living out of his farm, clearing his rent, or the interest 
on his capital, and acquiring some property besides, this 
alone is proof positive of the soundness of the systenL 



THEORETICAL AND PRACTICAL AGRICULTURE. 189 

When lie happens to remark a falling off in his wieat, 
clover, turnip, or potato-crops, he tries whether growing 
some other varieties on his fields will answer better, and 
attributes the diminished fertility of the soil to any and 
every event that may have occurred since he first remarked 
the decrease. Thus he will complain that his fields no 
longer yield the rich crops of former years, ever since the 
adjoining wood has been cleared ; or ever since the railway 
was made ; or the chemical manufactory established in the 
neighbourhood ; or he will attribute the falling off to the 
injurious influence of the numerous thunderstorms in the 
preceding year ; or to any other imaginable or imaginary 
cause — except always to himself and his system; the idea that 
the fault might possibly lie with him or his system can find no 
'place in his mind ; for, has he not pursued the same system 
for years with the very best results; his dungheap is as 
large as ever, and the land does not look changed in the 
least ? 

As a trader he is in the position of a shoemaker who 
must not devote his attention to investigations into the 
origin of sole and other varieties of leather, the process of 
tanning, and the properties which constitute the good qua- 
lity of the article, and who, were he to do so, would most 
likely supply the public with boots and shoes, neither cheap 
nor overwell made. The true shoemaker who thoroughly 
understands his craft, does not trouble his mind about such 
matters ; he leaves to others, whose special business it is, 
the task of studying them ; if he happens to be a man of 
some education, he studies the anatomy of the foot, and 
makes shoes that shall delight the female eye, and boots 
that shall not distort the shape of the foot, nor pro- 
duce corns. Such a pearl of a shoemaker would never 
dream of disputing with the man of science about leather, 
pitch, and thread, as he would have no time for such dis- 



1-AO THEORETICAL AND PRACTICAL AGRICULTURE. 

cussions ; lie would, on the contrary, be grateful to the che- 
mist for teaching him how and by what marks or signs to 
know and select the sorts of leather for soles and uppers 
best suited for the purposes for which they are severally 
intended. 

The scientific farmer and teacher of husbandry has a 
higher task assigned him. It is for him to rise above the 
mere routine teachings of empiric observations; to guide 
and keep the practice of farming in the right path ; to sub- 
ject to a rigorous and searching investigation the methods 
of husbandry adopted and pursued by the empirical farmer, 
in order to point out to him the why and wherefore, and 
to lead him to a proper sense and rational appreciation 
of his doings, and their results and consequences. The 
rational agriculturist has to inquire whether his system ac- 
cords with established truths and natural laws, or is in 
opposition to them ; and above all, he must never lose 
sight of the one great principle, that the aim of true prac- 
tical husbandry must be directed, not merely to the pre- 
sent production of the largest crops, but to the securing of 
a constant return of such crops. 

K the teacher of husbandry, instead of assisting and sup- 
plementing in this way the practice of agriculture, indulges 
in views that are simply calculated to vindicate the farmer 
in his empirical proceedings; — if, whilst clearly seeing that 
this empirical system of husbandry is opposed to established 
natural laws, he draws therefrom the conclusion that these 
natural laws may possibly not apply to practical farming, 
and that agriculture accordingly may not be subject to 
natural laws ; — if he asserts that the practice of husbandry 
and the science of agriculture may be treated as separate 
and distinct questions, and that a thing may possibly be 
true in science that is false in practice^ — if such are the doc- 
trines propounded by him, he stands as an agriculturist far 



THEORETICAL AND PRACTICAL AGRICULTURE. 141 

below the practical farmer, who fails to derive instruction 
from these lessons, simply because he finds in them nothing 
but a reflex of his own doings in the cultivation of his land, 
garnished with misconceptions and false views. 

A simple comprehensive natural law governs the greater 
or less abundance, and the longer or shorter succession and 
continuance of the crops that can be grown on a field. 
The greater or less abundance of the yield of a field de- 
pends upon the aggregate sum of the conditions of fertility 
therein existing ; the longer or shorter continuance and suc- 
cession of the crops that may be grown thereon, depend 
■upon the unaltered condition of this aggregate sum. 

A practical agriculturist, Albrecht Block, is reported to 
have said: "J. farmer can afford to sell and permanently 
alienate only that portion of the produce of his farm which 
has been supplied by the atmosphere — a field from which no- 
ting is abstracted can only increase^ not decrease in productive 
powery If we express the same idea in another form, viz., 
^'' A farmer m.ay sell and permanently alienate all that portion 
of the produce of his farm which has been supplied by the 
atmosphere — a field from which something is permanently 
taken away, cannot possibly increase or even continue equal in 
productive power,'''' the axiom thus enunciated is simply a 
natural law. In this opinion of this truly experienced man, 
to whom future agriculture will surely raise a monument, 
is at once expressed the whole foundation and groundwork 
of rational farming, and all the knowledge that the science 
of nature can teach the practical farmer. 

Every act of the farmer which violates the laws of na- 
ture, must justly be branded as an act of spoliation. 

If a farmer grows in three several fields alternately pota- 
toes, corn, and vetches or clover, or on one and the same 
field successively potatoes, corn, and vetches, and sells the 
produce obtained — the corn, the potatoes, and the vetches, 



142 THEORETICAL AND PRACTICAL AGRICULTURE. 

and continues to act in this manner for many years^ without 
manuring his land, the humblest peasant will predict the 
inevitable end of such a system ; he will tell him that a 
continuance of this kind of farming is impossible for any 
length of time. Whatever grass, corn, tuber, or other crop 
may be selected, and in whatsoever rotation, — the field will 
ultimately be brought to a state of exhaustion by it ; the 
corn will only yield an amount equal to the original seed, 
the potatoes will no longer produce tubers, and the vetches 
or the clover will die away after barely appearing above 
ground. 

These facts undeniably demonstrate that there exists no 
plant that could possibly be said to husband the resources of 
the soil, and a fortiori^ none that can possibly be had to 
enrich it. 

Innumerable facts have taught the practical farmer, that, 
in many cases, the successful cultivation of an after-crop on 
a field depends upon the nature of the preceding crop, and 
that it is by no means a matter of indijfference in what suc- 
cession or rotation he grows his crops. The previous cul- 
tivation of some underground crop, or some plant with 
extensive root ramifications, will tend to make the soil 
more favourable for the subsequent growth of a cereal. 
The latter will in such cases thrive better, and it will do 
so without the use (with the sparing application) of manure, 
and will yield a more abundant crop. But as regards 
succeeding harvests, there has been in reality no saving of 
manure, nor has the field increased in the conditions of its 
fertility. There has been no augmentation in the gross 
amount of the elements of food in the soil, but simply an 
increase of the available effective portion of these elements, 
and an acceleration of the results in a given time. 

The physical and chemical condition of the fields has 
been improved, but the chemical store has been reduced ; 



THEORETICAL AND PRACTICAL AGRICULTURE. 143 

all plants^ without exception^ exhaust the soil, each of them in 
its own way, of the conditions for their reproduction. 

There are fields that will yield without manuring for six, 
twelve, fifty, or a hundred years successively, crops of 
cereals, potatoes, vetches, clover, or any other plants, and 
the whole produce can be carried away from the land ; but 
the inevitable result is at last the same, the soil loses its 
fertility. 

In the produce of his field, the farmer sells. in reality his 
land ; he sells in his crops certain elements of the atmo- 
sphere that are constantly being replaced from that inex- 
haustible store, and certain constituents of the soil that are 
his property, and which have served to form, out of the 
atmospheric elements, the body of the- plant, of which they 
themselves also constitute component parts. In altogether 
alienating the crops of his fields, he deprives the land of 
the conditions for their reproduction. A system of farm- 
ing, based upon such principles, justly deserves to be 
branded as a system of spoliation. Had all the constituents 
of the soil, carried off from the field in the produce sold, 
been, year after year, or rotation after rotation, completely 
restored to the land, the latter would have preserved its 
fertility, to the fullest extent ; the gain of the farmer would, 
indeed, have been reduced by the re-purchase of the alien- 
ated constituents of the soil, but it would thereby have 
been rendered permanent. 

The constituents of the soil are the farmer's capital ; the 
elements of food supplied by the atmosphere, the interest 
of this capital : by means of the former, he produces the 
latter. In selling the produce of his farm, he alienates a 
portion of his capital and the interest ; in returning to the 
land the constituents of the soil removed in the crops, he 
simply restores his capital to his field. 

Every system of farming based on the spoliation of the 



144 THEOKETICAL AND PRACTICAL AGRICULTURE. 

land leads to poverty. The countrj in Europe which, in 
its time, most abounded in gold and silver, was, neverthe- 
less, the poorest. All the treasures of Mexico and Peru 
brought to Spain by the richly laden silver fleets, melted 
away in the hands of the nation, because the Spaniards had 
forgotten, or no longer practised, the art of making the 
money return to them, which they had put into circulation 
in commerce to supply their wants ; because they did not 
know how to produce articles of exchange required by 
other nations, who were in possession of their money. 
There is no other way of maintaining the wealth of a nation. 

It is not the land in itself that constitutes the farmer's 
wealth, but it is in the constituents of the soil, which serve 
for the nutrition of .plants, that this wealth truly consists. 
By means of these constituents alone, he is enabled to pro- 
duce the conditions indispensable to man for the preserva- 
tion of the temperature of his body, and of his ability to 
work. Rational Agriculture^ in contradistinction to the 
spoliation system of farming, is based upon the principle 
of restitution ; by giving back to his fields the conditions of 
their fertility, the farmer insures the permanence of the 
latter. 

The deplorable effects of the spoliation system of farming 
are nowhere more strikingly evident than in America,'* where 
the early colonists in Canada, in the State of New York, in 
Pennsylvania, Virginia, Maryland, &c., found tracts of 
land, which for many years, by simply ploughing and sow- 
ing, yielded a succession of abundant wheat and tobacco 
harvests ; no falling off in the weight or quality of the 
crops, reminded the farmer of the necessity of restoring to 
the land the constituents of the soil carried away in the 
produce.* 

* New York.— In the debate on the Bill passed by the Lower House of 



THEORETICAL AND PRACTICAL AGRICULTURE. 145 

We all know what lias become of these fields. In less 
than two generations, though originally so teeming with 

Congress, by which a grant of six million acres of Union land is made to the 
several States, for the establishment and maintenance of agricultural and in- 
dustrial schools, the mover of the Bill, Mr. Morrill, of Vermont, showed, in a 
most excellent speech, by means of exact statistical returns, how urgently 
these schools are required for the better education of our farmers, who at 
present, it would appear, are guilty of the grossest Vandalism in the manage- 
ment of their land. The speaker showed that we in America are far behind 
Europe in agriculture in general, and more especially in the modern scientific 
system of farming ; and that the sad results of this state of things are even 
now becoming manifest to an alarming extent. The honourable gentleman 
said, the general method of husbandry pursued in all parts of the Union was 
so bad and imperfect, that it must necessarily year after year more and more 
impoverish the soil ; and the incessant drain on the natural productive power 
of the soil amounted simply to downright robbery, committed by individuals 
at the expense of the national property. 

The following table in some measure shows the falling off that has taken 
place within a period of ten years in the annual yield of agricultural produce 
in several of the Northern States. The number of bushels of wheat produced 
was in 

1840 1850 

Connecticut 87,000 41,000 

Massachusetts 15*7,923 31,211 

Rhode Island 3,098 49 

New Hampshire 422,124 185,658 

Maine 848,166 269,259 

Vermont 495,800 585,955 



Sum total . 


. 2,014,111 


1,063,132 




Potatoes. 


Connecticut 


. 3,414,238 


2,689,805 


Massachusetts .... 


6,385,652 


3,385,384 


Rhode Island .... 


911,973 


651,029 


New Hampshire 


6,206,606 


4,304,919 


Maine 


10,392,280 


3,436,040 


Vermont 


8,896,751 


4,951,014 



Sum total . . . 35,207,500 19,418,19 



146 THEORETICAL AND PRACTICAL AGRICULTURE. 

fertility, they were turned into deserts, and in many dis- 
tricts brought to a state of such absolute exhaustion, that 

In many Southern States this falling off in the produce of the soil is equally 
significant. The number of bushels of wheat produced was in 



Tennessee . 

Kentucky . 
Georgia 

Alabama . 



Sum total 



1840 


1850 


4,569,692 


1,616,386 


4,803,162 


2,142,822 


1,801,830 


1,088,534 


838,052 


294,044 


12,012,736 


6,141,186 



These figures show pretty conclusively that in all parts of the Union the 
land must have been deprived of some of its most essential elements, and that its 
fertility is constantly on the decrease. In the State of New York there are 
now 300,000 sheep fewer than thirty years ago. Within a period of five 
years the decrease in the number of sheep in the State of New York 
amounted actually to nearly 50 per cent, and in the number of horses, 
cows, and swine to above 15 per cent. In 1845 the wheat crop in the State 
of New York amounted to 13,391,770 bushels; it has since then fallen off 
year after year, and last year it actually did not exceed 6,000,000 bushels. 

The average produce of Indian corn was in 1844, 2475 per acre, in 1854 
it was only 21-02. The average yield of wheat was in Virginia and North 
Carolina, in the year 1850, no more than seven bushels per acre, and in Ala- 
bama five bushels. "While the cotton crops in the new territories of Texas 
and Arkansas yield annually an average produce of 700 to 750 lbs. per acre, 
the old fields of South Carolina produce only half as much. The tobacco 
crop of Virginia was 18 million lbs. less in 1850 than in 1840. No kind of 
crop has proved so injurious to the fertility of the soil as that of tobacco, and 
in many of the States whole tracts of land are now lying waste, that for a 
century had been made to yield, year after year, crops of tobacco, maize, and 
wheat. There can be no doubt but that three-fourths of the arable soil of 
the Union are undergoing, to a greater or less degree, this exhaustive pro- 
cess. Dr. Lee, of Georgia, estimates the decrease in the annual produce of 
the soil of 100 million acres of land in the United States, at ten cents per 
acre. This would give a total of 10,000,000 dollars, making the amount lost 
equal to a capital of 166,666,666 dollars — a larger sum than all our federal 
and states taxes together. 

In other branches of husbandry also enormous losses are caused by the 
want of proper information on many essential points — a want which can only 
be remedied by the establishment of agricultural schools. One of the ablest 



THEORETICAL AND PRACTICAL AGRICULTURE. 147 

even now, after having lain fallow more tlian a hundred 
years, they will not yield a remunerative crop of a cereal 
plant. 

As every agriculturist in Europe has a notion that his 
system is an exception and better than that of others, and 
that, judging from his own experience^ his fertile fields require 
no restoration of mineral matters to keep them up to the 
proper degree of productive power, so every early colonist 
also believes at first that his land, for the crop which he 
grows on it, forms an exception to other fields. He also 
trusts to his experience to insure an infinite succession of 
rich harvests ; but even ere his children are grown up, he 
finds out his mistake. His farm passes into the hands of 
another colonist, who continues to despoil the soil in the 
same way as his predecessor, only with a larger expenditure 
of capital and labour. When he, in his turn, perceives that 
the plough will no longer sufiice to keep the yield up to the 
former height, the land is then finally handed over to the 
tender mercies of the German colonist, who has been taught 
to look upon dung as the soul of agriculture, — a maxim of 
specious wisdom, of which his predecessor knew nothing, 
and the new owner then sets about despoihng the soil after 
his own fashion.* 

agriculturists in Massachusetts estimates the annual loss to the States, in 
cattle of all kinds, and in the produce of the dairy, &c., at several millions. 
There are about 447,014 horses in the State of New York, on which, from 
the prevailing ignorance of the veterinary art, there is an annual loss of not 
less than two million dollars. 

These statistics could not, of course, fail to produce the impression intended, 
and the House gladly entertained the motion to establish agricultural and 
industrial schools. It would be a pity if the Senate should not be able to find 
time before the approaching adjournment to discuss and adopt the measure. 
— AUgemeine Zeitung, No. 175. Supplement of June 24, 1858. 

* " Agriculture, in so far as I had occasion to inquire into the matter, is in 
a most primitive and unsatisfactory state in the province of Minas Geraes. It 
consists simply of a system of downright spoliation, disproportionately large 



148 THEORETICAL AND PRACTICAL AGRICULTURE. 

The European system of cultivation, called high farming^ 
is not that open system of robbery of the American farmer, 
followed by the utter exhaustion of the soil ; but it is a more 
refined species of spoliation, which at first glance does not 
look like robbery. It is spoliation accompanied by self- 
deception, veiled under a system of teaching, the very basis 
of which is erroneous. 

The simplest peasant has sense enough to see, and all 

quantities of the mineral constituents being constantly taken off, without the 
restoration of any portion whatever. Thus, for instance, they make a so-called 
Roca^ i. e., the trees and underwood are cut down on a certain tract, and 
towards the end of the dry season burnt on the spot ; three or four harvests 
are then taken from the land so prepared, and it very often occurs that among 
these there are two Indian-corn crops in immediate succession. After this 
the field is allowed to lie fallow until it is again sufficiently covered with 
brushwood, when the same process is repeated ; the interval varying between 
three and twelve years, according to local conditions and to the wants of the 
proprietor. It is quite evident, that the soil here has never had restored to it 
the smallest portion of the mineral constituents removed by the crops. No 
wonder, then, that there should be universal complaints in the province of the 
constantly increasing sterihty of the Bocas. One of the more intelligent 
planters of the province told me that, of all the plants grown there none 
showed so large a falling off as the sugar cane, and that he at present reaped, 
on the same Bocas, only a third of the produce obtained by his father 55 to 60 
years ago ; and yet, he remarked, somewhat naively, he was much better off 
with his small crop, than his father had been with the larger one, for the 
latter (his father) had barely been able to realise a milreis for the cask of 
Cachaza (brandy), whereas he himself had last year received 14 milreis for the 
same. Now this man was perhaps right in his way ; but how will it fare 
hereafter with his son, if he continues the same system, and the price of 
Cachaza happen to fall again ? In the province of Bahia, the falling off in 
the sugar-cane crops is so great, that about a twelve month since a number of 
planters combined to send out a ship to bring from several distant ports new 
sorts of sugar-cane. They attributed the falling off in the produce of their 
plantations simply and solely to the degeneration of the cane, without reflect- 
ing that by the incessant cultivation of the plant on a large scale, their land 
had been most enormously drained of the conditions of its fertility." — J.J. von 
Tschudi's Journey through the Province of Minos Geraes. — Allgemeine Zeitung, 
No. 47, May 21, 1858. Supplement. 



THEORETICAL AND PRACTICAL AGRICULTURE. 149 

agriculturists agree with him, that clover, turnips, hay, &c., 
cannot be sold off from a farm, without most materially 
damaging the cultivation of corn. Every one willingly 
admits that the sale and exportation of clover, turnips, &c., 
exercise a detrimental influence on the growing of corn. 
" Above all, let us take care to have plenty of fodder, the 
corn crop will then take care of itself" But that the exjpor- 
tation of corn may possibly exercise an injurious influence on 
the cultivation of clover or turnips, that it is above all 
indispensable to restore to the soil the mineral constituents 
of the corn^ to enable the clover or turnip crop in its turn to 
" take care of itself," — in other words, that in order to grow 
clover, turnips, &c., we must manure the land — this is a 
notion utterly incomprehensible, nay absolutely impossible, 
for most agriculturists. For, is not the clover grown for 
the sake of the manure ? What advantage, then, would 
there be if it were necessary to manure again to produce the 
clover ? This clover the farmer expects to grow for nothing. 
From this total misapprehension of the very foundation of 
all true industry, spring all the errors and defects of the 
prevailing system of cultivation. 

The mutual relations existing in the order of nature 
between the two classes of plants, are, however, as clear as 
daylight. The mineral constituents of the clover, turnips, 
&c., and of the corn, form the conditions for the production 
of the clover, turnips, &c., and of the corn, and they are in 
their elements quite identical. The clover, turnips, &c., 
require for their growth a certain amount of phosphoric 
acid, potash, lime, magnesia — so does the corn. The mineral 
constituents contained in the clover are the same as those in 
the corn, plus a certain excess of potash, lime, and sulphuric 
acid. The clover draws these constituents from the soil ; 
the cereal plant receives them — we may so represent it — 
from the clover. In selling his clover, therefore, the farmer 



150 THEORETICAL AND PRACTICAL AGRICULTURE. 

removes from his land the conditions for the production of 
corn ; no mineral constituents are left for the corn. If, on 
the other hand, he sells his corn, there will be no clover crop 
in the following year ; for in his corn he has sold some of 
the most essential conditions for the production of a clover 
crop. 

The peasant expresses in his own way the part which the 
cultivation of clover and other fodder plants performs in 
the economy of his land, when he tells us that he regards, 
as a self-evident proposition, that a farmer must not sell 
his stable manure ; that without manure a continued culti- 
vation of his farm is impossible ; and that a farmer who 
sells his clover and other fodder plants, does actually sell 
his manure, and that there is no need of the wisdom of the 
chemist to make him understand this. This is very true ; 
for so far as that goes, the common sense of the simplest 
peasant will guide him. But that a farmer, in selling his 
corn, is still actually parting with his manure, would, how- 
ever, appear to be beyond the comprehension of the great 
majority of the most enlightened agriculturists. The dung 
contains all the mineral constituents of the clover and 
other fodder plants, and these consist simply of the mineral 
constituents of the corn, plus a certain quantity of potash, 
lime, and sulphuric acid. Now, as the whole dung-heap 
consists of parts, it is quite evident that the farmer must 
not sell any part thereof; and that, if it were possible to 
devise a means of separating the mineral constituents of 
the corn from the others, those very mineral constituents 
so separated would have the very highest value for the 
farmer, as they form the most essential condition for the 
production of corn. Now, in the cultivation of corn this 
separation is actually effected, for these mineral constitu- 
ents of the manure are converted into constituents of corn. 
In selling the corn produce of his fields the farmer parts, 



THEOKETICAL AND PRACTICAL AGRICULTURE. 151 

therefore, with a portion, and, indeec, with the most effi- 
cient portion of his manure. 

Two dung-heaps of equal appearance, and seemingly 
equal quality, may have a very dissimilar value for the 
cultivation of corn ; if one of the heaps contain twice as 
much mineral constituents of corn as the other, it has 
double its value. By the exportation of the mineral con- 
stituents of corn, which the latter had drawn from the 
manure, the dung of the farm is made to suffer a progres- 
sive diminution of its efficiency for future corn crops. 

In whatever light, therefore, we may look upon the 
exportation of corn, or any other produce of the fields, to 
the farmer who omits to restore to the soil the mineral 
constituents removed from it, the ultimate result will 
always be exhaustion of his land. The continued expor- 
tation of corn renders the soil unproductive for clover, or 
deprives the dung of its efficacy. Dung, in itself, has an 
agricultural value only in so far as it contains the conditions 
necessary for the growth of the saleable produce ; the mere 
size or extent of a dung-heap does not constitute its value. 

The reader will now understand what a total want of all 
knowledge there is in the precept, that dung is the raw 
material to be worked and made into produce by agricultu- 
ral industry ; and how essentially that axiom and opinion 
have contributed to blind the eyes of agriculturists to the 
clear perception of the sole and original source of all 
agricultural production, and of their own prosperity — viz.^ 
the soil. 

If our farmers had to till the teeming virgin soil of 
America, Australia, or New Zealand, a professor of agri- 
culture, who would try to persuade them that " manure is 
the soul of agriculture," would simply appear ridiculous in 
their eyes, as their own experience would show them that 
the fields yield rich harvests without manure. 



152 THEORETICAL AND PRACTICAL AGRICULTURE. 

In our exhausted fields tlie roots of the cereal plants 
find no longer, in the upper layers of the soil, a sufficiency 
of food for a full crop ; the farmer, therefore, grows on 
these fields clover, turnips, and other plants, which, with 
their wide-spreading and deep roots, penetrate through the 
soil in all directions, and by the great surface of their roots 
render available, and assimilate to themselves, those con- 
stituents of the soil which the culmiferous plant requires 
for the formation of seed. 

In the remains of the roots, stalks, leaves, and tubers of 
these plants, which the farmer puts in the form of manure 
on the upper layers of his soil, he returns to it in a concen- 
trated form the deficient corn constituents required for one 
or several full crops. These indispensable elements of 
food, which were before scattered throughout the subsoil, 
have by the green crops been collected from it and added 
to the surface soil. In effecting this object, the clover and 
fodder plants can no more be regarded in the light of 
creating the conditions necessary for the larger corn crops, 
than the rag-gatherer, who collects the materials for manu- 
facturing paper, can be looked upon as the producer of 
those rags. 

The American farmer despoils his field without the least 
attempt at method in the process? When it ceases to yield 
him sufficiently abundant crops, he simply quits it, and 
with his seeds and plants, betakes himself to a fresh field ; 
for there is plenty of good land to be had in America ; 
and it would not be worth his while to work the same field 
to absolute exhaustion. But our modern system of " high 
farming" is an organised system of spoliation — ^the last, 
highest, and most finished degree of the art of wearing out 
the soil. 

Before the thirty years' war the population of Germany 
was not smaller than at present. Every individual naturally 



THEORETICAL AND PRACTICAL AGRICULTURE. 153 

required at that time for breathing and working, the same 
supply of oxygen and of the elements of muscular force as 
people require at present for the same purpose. The agri- 
culturist of that day pursuing the same spoliation system as 
the American farmer of our day, produced the same supply 
of carbonaceous and nitrogenous food as is grown at pre- 
sent ; only he took m^ore time to do so. There were years of 
scarcity, the effects of which were more severely felt then 
than they are now, because they were not mitigated at that 
time by a supply of the deficiency from America, Hungary, 
or the great granary of South Eussia; but in ordinary 
years the land produced plenty. One year. Winter corn 
was grown ; the next year, Summer corn and turnips {Stop- 
pelruhen) ; the third, the field was allowed to rest ; there 
was no other rotation except with pulse. What is now- 
a-days called stall-feeding, was entirely unknown. The 
meadow supplied winter fodder for horses ; cattle and 
sheep found their food on the commons or fallows, and in 
the woods. The agricultural system of that period might 
be likened to the system of the man who had an income of 
one florin a day, and who let the florins of one week accu- 
mulate in order to spend them in the next week. On 
Sunday he found himself accordingly with seven florins in 
his pocket, and could therefore now afford to spend on the 
Monday following four florins ; on Tuesday, three florins ; 
and on Wednesday, other three florins, and in this manner 
was able to buy a number of things which he would have 
been unable to procure with a daily expenditure of one 
florin. 

The system of letting the land lie fallow every third / 
year did not make the soil more fertile, or add to the ele- ' 
ments and conditions of its productiveness ; but it served ; 
to render those elements and conditions more available 
within a certain time. Except by conveying to it a supply \ 

7* 



154 THEORETICAL AND PRACTICAL AGRICULTURE. 

of fertilising material, it is quite impossil le to make a field 
richer and permanently more productive. That the field 
did yield a more abundant crop after having lain fallow 
was owing simply to the fact that the soil still contained a 
sufiicient store of effective mineral constituents, only not in 
a state available or assimilable for the roots. The rest 
enjoyed by the field during fallow afforded time for part 
of their store to be made available as food, and in this way 
a remunerative crop was obtained. The overplus of the 
more abundant harvest which follows a period of fallow, is 
not a real addition to the revenue yielded by the field, but 
simply a saving from the preceding year, when the land 
was at rest. By means of this system the soil is somewhat 
more profitably despoiled of its resources, as the work of 
spoliation proceeds more leisurely. Time, people argued, 
costs no money, and fallow saves manure, an advantage 
which was clear to all. This system prevailed till towards 
the middle of last century. The peasantry, as a body, fell 
into a state of poverty and wretchedness, and the production 
of the fields continued decreasing. 

In the seventeenth and the beginning of the eighteenth 
century, the culture of the vine was still flourishing in 
countless places in Germany ; fields upon fields were then 
occupied by vineyards where the grape now no longer 
grows; the large tithe-cellars alone, which still continue 
to exist in many places, give evidence of the immense 
extent of the vine culture in by-gone days. With the 
vineyards the spoliation system of cultivation sooner pro- 
duced its results; for vineyards produce no manure, and 
as the corn growers found that the cultivation of their own 
fields stood in the utmost need of all their manure, the 
culture of the vine necessarily died out, like the flame of a 
lamp for want of a supply of oil. 

"The only winter-food the farmer had for his cattle, 



THEORETICAL AND PRACTICAL AGRICULTURE. 155 

besides bad and sour meadow-lierbage, consisted of white 
turnips, carrots, cabbage and potatoes ; and even of these 
there was no great store, because the fields had ceased to 
produce when unmanured. This scanty food was, through- 
out the whole winter, whilst it lasted, made still scantier by 
steeping and boiling to eke it out, and when at last it came 
to an end, the cattle had to starve on barley, oat and pease 
straw. The milk, butter, and cheese yielded in return were 
little in quantity and wretched in quality. The coming of 
spring was anxiously awaited to get a few cuttings of the 
young wheat shoots, and the cattle were sent to the com- 
mon to feed on grass barely a couple of inches high, whence 
the poor beasts returned at night just as famished as when 
they had left the stable in the morning, looking like the 
lean kine that Pharaoh saw in his dream." This is the 
description given of the then state of agriculture in Ger- 
many by John Christian Schubert, whom the Emperor, 
Joseph n., created a Knight of the Holy Eoman Empire, 
bestowing upon him the style and title of Ritter von 
Kleefeld (Knight of Cloverfield), as a mark of imperial 
appreciation of the eminent services rendered by him in the 
introduction of the cultivation of clover into Grermany. 

The new culture introduced by the worthy Knight was 
hailed with acclamation all over the Empire. The peasants 
who grew clover received silver "clover-dollars," to wear 
round the neck. Stercutius^^ the God of Manuring of 
Ancient Rome, whose worship had been abandoned for 
2000 years, was replaced on his throne: in Agricultural 
Educational Institutions altars were raised to him, at which 
his priests even to this day continue to sacrifice. But the 
God of the Dunghill proved capricious. He seemed to 



* Stercutius, or Sterquilinus, according to some, one of the names of 
Saturnus. (See Virgil's "Georgics," by Voss, page 74. 



156 THEORETICAL AND PRACTICAL AGRICULTURE. 

make some fields the special objects of his bounty, only to 
forsake them again after a time ; and now, after a hundred 
years' sway, he has grown altogether stern and unkind. 
He no longer bestows his former rich gifts even upon his 
most assiduous worshipper, and from the very fields which he 
once seemed most to favour, he now withholds the power of 
producing the poorest crop of manuring plants. Therefore 
do his priests urgently supplicate for a small piece of the 
philosopher's stone to be offered as an oblation to the God 
of Manure, thai he may relent, and make clover for manur- 
ing grow for the future on fields on which that plant will 
now no longer thrive. When at a later period the potato 
and the application of marl and gypsum to the land came 
to aid the beneficial efforts of the cultivation of clover, 
people trusted there would now be an end for ever to all 
want. The old spoliation system, first in its naked form, 
and then altered by the introduction of fallow, now under- 
went a further modification, based on the system of a well- 
known highwayman on the borders of the Ehine. He 
stripped the rich of their dollars, bestowed at times a 
penny on the poor, and for sport cut the buttons off their 
breeches. 

According to his creed the wealth of the rich had been 
stolen from the poor, and it was but justice therefore to 
make them disgorge it. 

Our high farmer acts upon a similar principle. In his 
corn crops he makes the (rich) clover disgorge, as it were 
the dollars which it has extracted penny by penny from the 
(poor) field ; and he fancies this system of robbery will last 
for ever, as his instructors have taught him that his land 
possesses the property of sweating penny pieces. 

The consequence of this spoliation system upon the 
principle of the noble robber are clear, patent, and obvious 
to everybody; never has the want of manure been more 



THEORETICAL AND PRACTICAL AGRICULTUJIE. 157 

severely felt than at present. All the ways and means 
which so marvellously tended towards the end of last cen- 
tury to increase the productiveness of the land, are at pre 
sent resorted to in vain ; they fail to produce their former 
effect. The application of gypsum to the soil now makes 
the clover only more watery, without increasing the crop ; 
land treated with marl is more unproductive than before. 
Were it not for the manure which the trees of the forest 
yield in many countries, the culture of the cereals would, 
in many former fertile districts, long since have come to an 
end, like that of the vine. The agriculturist in these parts 
now despoils the woods, as he formerly despoiled his fields, 
and he will continue this new system of depredation as 
long as it will answer ! "If you will grow clover, and will 
strictly follow my directions," said the good Schubert to the 
peasants of his t;me, "you will have ample cause for 
rejoicing and for praising the Lord out of the fulness of 
your heart for his rich blessings. But bear in mind one 
rule, which I charge you now once for all to follow ; never 
grow clover at the expense of corn, but grow it only in 
fallow, that it may cost you nothing — in other words, give 
up the practice of letting a field lie fallow." At that time 
there was no other system of husbandry known but the so- 
called " Three-fields-system," or system of triennial rota- 
tion. In twelve years cereals were grown eight times in a 
field, and clover four times. Where are those glorious 
days when the same field yielded in three years two crops 
of corn and one of clover into the bargain ! Kow-a-days 
high farming produces in twelve years only six corn crops. 
In Mecklenburgh good land gives only four com crops in 
nine years. The original area on which fodder plants 
were cultivated, and which at the time proved amply suffi- 
cient to collect and concentrate the food required for the 
cereals, is therefore no longer large enough to keep up the 



158 THEOKETICAL AND PKACTICAL AGRICULTURE. 

supply, and it has become necessary to extend it. The cul- 
tivation of food for cattle takes up at present as great, and 
even a greater breadth of land than the raising of food for 
man ; and men's minds and ideas have become so perverted, 
that this lamentable fact is actually looked upon in the 
light of a great improvement ! 

So long as those most interested in the matter, instead 
of reflecting upon the conditions on which the successful 
cultivation of all plants depends, and trying to discover 
these conditions and to understand their application in 
practice, seek to put agriculture into a healthy condition 
by " manure," a thing so very indefinite, indefinable, and 
variable in its nature, no real progress can be expected. 
For my part, I am quite aware, that science will for a long 
time to come have to preach to deaf ears. So long as agri- 
culturists derive from the spoliation of their own lands 
plentiful crops and a good income, there is no hope of the 
advent of a more rational system of husbandry. The field 
is to such men, simply a cow that gives them milk, but 
which they would feed with its own flesh, taken from its 
ribs ; and the folly of such a proceeding will strike them 
only when the light shines through the hollow skeleton of 
their victim. Man is naturally prone to spoliation, and 
dreads nothing so much as to have to exert his mental 
faculties in the acquisition of what he needs ; he is in 
many respects like a child in whose eyes the school and 
learning are the greatest of all troubles. ISTecessity is the 
only compulsory agent that will ever make him move, and 
this will come soon enough. 

The dangers threatening the state and society from the 
wanton sjDoliation of our woods, led to the devising of our 
(German) present most admirable regulations for the 
management of our woods and forests. If our for'gsts 
were parcelled out into as many portions and divided 



THEORETICAL AND PRACTICAL AGRICULTURE. 159 

among as many foolish hands as our arable land, we should 
long ago have been without wood. There is the most 
imminent danger just now, that the rapidly progressing 
destruction of the Quinine or Peruvian bark-tree will, at 
no distant period, deprive society of one of the most inva- 
luable medicinal agents ; and our only consolation is, that 
when the last tree of the kind shall have fallen, the rational 
culture of the plant will then begin which after a certain 
number of years will again provide us with a permanent 
supply of Bark.* 

The expedients hit upon by certain writers on husbandry 
to shut the eyes of agriculturists and their own, to the light 
of science, and to make the comprehension of the laws of 
the nutrition of plants inaccessible to the mind and under- 
standing, are truly most remarkable ; and the history of 
agriculture will surely preserve the memory of them. To 
this day the farmer of the Wetterau justly regards the sale 
of his manure, not only as a disadvantage, but as a positive 
shame: it is an object of ambition with him to raise the 
largest possible amount of it on his fields. He has been 
taught that there is in manure a certain inconceivable and 

* It is asserted that our high farmers " know the art of extracting from the 
same piece of land more grain than could be got from it in the seventeenth 
century." I doubt the correctness of this assertion, and think it quite within 
the limits of possibility that accurate statistical researches might prove the 
very reverse to be the case. Those who can look back a generation will 
probably remember, as I do, that large tracts of land which now are culti- 
vated and bear produce, lay formerly waste (an advantage for which we are 
no doubt indebted to the rotation system). The question arises here wlie- 
ther, admitting the production to be larger now than formerly, the increase 
is not rather owing to the simple fact that the extent of producing surface is 
now considerably greater than it was. A distinguished American Economist, 
Carey, assures me, that accurate statistical inquiries instituted in 1850 by the 
'' Times" Commissioner have shown that England at that time produced 
actually 2,000,000 quarters of corn less than in 1774, according to Arihui 
Young. I will not venture to guarantee this fact, which, if true, would cer- 
tainly look very significant. 



160 THEORETICAL AND PRACTICAL AGRICULTURE. 

indefinable something which is to be met with in manure 
alone, and in no other matter ; — that ash and gypsum are 
not food for plants, but serve, like the whip of the carter 
to his lazy horse, to stimulate the activity of sluggish 
plants. Even up to the present time, they look upon the 
mineral constituents in guano and in bone earth, as not in 
the slightest degree contributing to the nutrition of plants, 
but simply as auxiliary stimulants applied to the soil for the 
purpose of promoting the production of stable dung. 

The worshippers of manure act in defence of their notions 
in a somewhat similar way to the Birkenfeld peasantry of 
last century, who grievously complained that government 
wanted to compel them to cultivate a foreign weed (clover). 
They told the officers in the plainest terms " to stick to 
their last, and concern themselves about things they had 
learned. As for husbandry, they (the peasants) were likely 
to know much more about it than all the margraves and 
overseers in the world." They did not wish to give the 
matter a single trial, and when ultimately compelled to 
sow the clover, they demanded, after a time, a magisterial 
inspection of their fields, and showed " that not a leaf of 
the clover had come up ; " and no wonder ; for it turned out 
at last, that the peasants had boiled the seed before putting 
it in the ground. In our day scientific principles are treated 
somewhat in a similar manner ; the professors of modern 
agriculture boil them in their pot, and it is then openly 
shown that not a grain has come up. These gentlemen 
will on no account consent to see farmers freed from the 
compulsory rotation of crops ; this they must understand 
much better than anybody does. But their own doctrine 
is barren, because it has no roots. Whatever good precepts 
their books contain, the agriculturist knows already, for 
these teachers derived their information from him ; but 
such precepts as originate with themselves, inspire the far- 



THEOKETICAL AND PKACTICAL AGRICULTURE. 161 

mer with no confidence, lead to no profitable ideas, do not 
increase his energies nor exalt his faculties. 

If they would confine themselves to simply telling the 
agriculturist what this or that farmer has at any time done 
on this or that field ; — that land requires to be well ma- 
nured; — that guano and bone-earth constitute excellent 
manures, and that Chili-saltpetre, gypsum, and marl are 
also not to be despised, — surely no one would blame them 
for disseminating these truisms. But they have gone much 
further, and in their blindness and shallowness have laid 
the axe to the very root of agricultural prosperity — and 
this can and must no longer be permitted. 

They maintain and teach that in guano. Chili-saltpetre, 
and bone-earth, nitrogen is the only common constituent 
that is deserving of consideration, and that it is to this ele- 
ment alone that increased productiveness is to be attri- 
buted. 

They teach and wish farmers to believe, that 10 to 12 
pounds of the urine of cattle, which contains no phosphoric 
acid, will produce the same effect as 1 pound of guano, 
which is rich in phosphoric acid, — simply because both sub- 
stances contain the same quantity of nitrogen. They teach 
and maintain that the fertilising action of guano and of 
farm-yard manure depends upon the same cause, viz., their 
amount of nitrogen, and that guano must produce the same 
effect as farm-yard manure. 

All this they maintain without adducing a single fact in 
support of their assertions, or having once sought to show, 
by some unexceptionable instance, that the application of 
nitrogen by itself can make an exhausted field yield for a 
number of years the same crops of corn or other produce 
that are actually got from it by the application of farm-yard 
manure, guano, and bone-earth. That nitrogen could really 
produce such an effect everybody at all acquainted with 



162 THEORETICAL AND PRACTICAL AGRICULTURE. 

the elementary principles of the nutrition of plants must 
know to be an actual impossibility. 

But these teachers go even much beyond this. In No. 
247 of the Swahian Mercury^ of the 15th October, 1856, 
there is an article on the Chili-saltpetre and its use, written 
by a Professor at one of the most renowned Agricultural 
Academies of Germany, in which the reader is told that 
''a hundredweight of Chili-saltpetre will produce the same 
effect as 75 to 80 cwts. of farm-yard manure, whilst a cwt. 
of guano will only be equivalent to 60 or 70 cwts. of the 
latter; — that a cwt. of Chili-saltpetre will produce about 
three cwts. of grain ; that its action, however, is only per- 
ceptible the first year; that its price is 12 florins (205.) per 
cwt., and that, accordingly, the corresponding value of a 
cwt. of farm-yard manure would be 9 krs. (3d)" 

This announcement may be said to be the very culminat- 
ing point of the theory of our teachers of modern agricul- 
ture ; it is evidently intended to induce the well-to-do pea- 
sant, and the small land-owner, who may be in want of 
manure, to buy Chili-saltpetre — a salt which contains none 
of the ash constituents of the cereals, but is composed sim- 
ply of nitric acid and soda; one cwt. of which, we are 
assured, will produce three cwts. of grain. Its effect, it is 
true, lasts only one year, but it will, nevertheless, prove 
equivalent to 75 or 80 cwts. of farm-yard manure, the bene- 
ficial action of which on a field may still be observed after 
seven or eight years. The simple comparing of Chili-saltpetre 
to guano and farm-yard manure is, in itself, an offence against 
common sense ; and the recommendation of that salt, at the 
expense of guano and farm-yard manure, is an injury in- 
flicted on the property of thousands by an unprincipled or 
ignorant adviser. 

A proceeding of the kind may be excusable in a com- 
mercial traveller soliciting orders for a speculator in Chili- 



THEORETICAL AND PRACTICAL AGRICULTURE. 163 

saltpetre ; but if we find that such notions are disseminated 
by teachers of agriculture and professors at agricultural 
institutions ; if we see those teachers intent upon making 
the farmer believe, by means of a spurious array of figures, 
entirely inapplicable in the great majority of cases, that 
nitrogen possesses for him twice the value of phosphoric 
acid, five times that of potash, and twelve times that of 
phosphate of lime — it is time for all sensible men to unite 
and call these teachers to account. We may surely demand 
of them what is only right and fair, viz., that they simply 
prove the truth of their theories by a faithful statement of 
accurately observed and properly guaranteed facts. 

Although it has, in these last years, been most plainly 
demonstrated to these men that their views and theories are 
founded in error, this has not brought conviction to the 
mind of a single individual. One after another has come 
forward with the vain and impotent attempt — not to adduce 
new and striking proofs in support of their doctrine — but 
to suggest doubts against the true import and bearing of the 
facts brought forward in refutation of their views. Not one 
of them has ever even dreamt of appealing, in support of 
the truth of his views, to his own numerous experiments 
and chemical analyses on which those views are based; 
because all of them know full well that their labour in this 
line will not bear the test of a rigorous scientific examina- 
tion. In their distress they now turn for help to the same 
agriculturists whom they had, by these analyses, persuaded 
that nitrogen was the only active agent in guano, bone- 
earth, and rape-dust, and appeal to them to bear witness 
that they have given them good advice, and that their 
theories have been borne out by practical experience ; that 
a pound of ammonia has a practical value of twelve groschen, 
a pound of bone-earth of only one groschen. But the prac- 
tical man, in truth, knows nothing of the action of ammo- 



164 THEORETICAL AND PRACTICAL AGRICULTURE. 

nia or of nitric acid, or, at all events, nothing but from 
hearsay ; for he has not been taught by the agricultural 
chemist that guano, bone-earth, and rape-dust are excellent 
manures, but the latter has, on the contrary, learned this 
fact from him, and has simply thrown in his own little 
hocus-pocus, that a few stray beams of the sunshine of their 
beneficial action might be reflected on him. 



LETTER XL 

Ammonia is an element of food indispensable to Plants — Comparison of the 
action of Water and Ammonia — Ammonia is an element of food and a 
Solvent of Mineral Matters in the Soil — Ammonia alone, or its Salts, useless 
to Plants, without Mineral Food — Vast amount of Ammonia in arable Soils 
— The " Nitrogen " theory of Manures — The error of attributing the chief 
value of a Manure to its Nitrogen — The reason v^hy the quantity of Nitro- 
gen in Guano and Excrements may be taken as a standard of their Agri- 
cultural value — Proper mode of Comparing the relative effects of Guano, 
Ground Bones, and Chili-saltpetre — The Loss of Fertilising matter in the 
Flesh and Grain carried to large towns; the constant loss of Phosphates in 
the Excrements of the inhabitants — The importation of Guano most 
inadequate to replace this loss — Superiority of Human Excrement over 
Guano as a Manure for Corn Fields — Tobacco, Potatoes, and Beet-root are 
more exhausting to a soil than Wheat — Injurious influence of extensive 
Cultivation of the Tine on the production of Com and Wheat — Effect of 
the Subdivision of the Land. 

As an element of food, ammonia is as indispensable to 
plants as carbonic acid ; a brief consideration of the part 
which water plays in the nutrition of plants will best enable 
us to understand the fertilising action of ammonia in 
manure. 

Water subserves a double purpose in vegetation ; it sup- 
plies to the plant in one of its constituents an indispensable 
element, and serves besides to render mineral matter in the 
soil fit for absorption by the roots. Though the soil be 
ever so rich in the elements of food for plants, still the latter 
will not grow in hot weather, if there be a deficiency of 
moisture in the soil; for the moisture in the soil is the 
channel through which mineral food has to reach the inte- 
rior of plants. 



166 THEOKETICAL AND PRACTICAL AGRICULTURE. 

When there is a failure in the supply of mineral food, 
the leaves absorb neither carbonic acid nor ammonia from 
the air; and vegetation is brought to a stand-still, although 
the air contains more moisture in hot days than in cold, — 
this moisture being of no avail to the plant. With a defi- 
ciency of water in the ground, sunny and warm days, 
which under other circumstances would be the most fa- 
vourable for growth, actually prove the most pernicious, 
particularly for summer plants, which have not yet had 
sufficient time to push their roots deep into soil where there 
still exists a supply of water that might convey food to 
them. In such cases barley grows barely a hand high and 
shoots into ear, and potatoes produce no tubers. One good 
shower at the right time changes this state of matters as if 
by magic. If the farmer could bring down rain upon his 
fields at the right time^ as the gardener can water his flower- 
pots, all plants would give a maximum yield, pre-supposing 
of course, that there is a sufficient available supply of food ; 
for if there be a deficiency of the latter in the soil, a corres- 
ponding diminution in the maximum yield must in conse- 

I quence be expected. Plants therefore absorb carbon and 
nitrogen in proportion as the water conveys to them more 

, of the mineral constituents of the soil ; their growth is accele- 

1 rated, and the weight of the crop increased. 

It is exactly the same with ammonia. K we increase the 
quantity of ammonia in the air or in the soil, the plant 
finds at 2^ favourable juncture a larger supply of this element 
of food than usual, and the consequence is, that a corres- 
pondingly larger amount of the mineral elements of food is 
rendered available. As the leaves of a plant can daily 
come in contact with only a certain volume of air, they 
can of course take up from it no more ammonia and car- 
bonic acid than this volume of air contains ; the absorption 
of these substances and the increase of the plant consequent 



THEOKETICAL AND PRACTICAL AGRICULTURE. 167 

thereon require accordingly a given time. If a plant 
every day absorb an equal amount of these elements of food, 
it will receive of course twice as much in two days as in one. 

If a plant on favourable days received twice or four 
times the usual supply of mineral food, the surplus must 
remain inactive until the leaves shall have taken up from 
the air sufficient carbonic acid and ammonia to combine 
with these mineral elements in the formation of constituent 
parts of the frame of the plant. None of the elements of 
food will act without the presence and co-operation of the 
others. If, accordingly, we increase the amount of ammonia 
in the soil, or in the air (of carbonic acid, there is generally 
no deficiency), the development of the plant will, the other 
conditions of its growth being equal, be considerably 
quickened; in other words, the plant will grow in bulk 
and substance much faster than under ordinary circum- 
stances. Familiar illustrations of this may be seen every 
day in hot-beds. Had the mineral elements of food not been 
present in the plant and available for its nutrition^ the ammo- 
nia would not have had the slightest effect on the increase 
of the bulk of the plant. 

It need then excite no wonder that the application of 
guano to a field should so largely increase the yield of 
corn ; for guano contains not only the mineral elements 
which a soil must possess to produce corn, but also in the 
ammonia an indispensable element of food, which serves to 
quicken their action and to shorten the time required for 
their assimilation. On many fields the ammonia in the 
guano may, if the weather prove propitious, possibly effect 
the assimilation of double the ordinary quantity of these 
mineral constituents, and thus render the amount of pro- 
duce yielded in one year equal to what would have been 
otherwise obtained in two years by these mineral matters 
alone. 



168 THEOKETICAL AND PRACTICAL AGRICULTURE. 

It is clear also that ammonia used by itself in a soil con- 
taining a sufficient supply of tlie elements required for the 
production of a corn crop, must exert a favourable action 
on the increase of the produce. But as in the large crop 
reaped, there is now removed from the field a greater pro- 
portion of the conditions upon the presence of which the 
efficacy of the ammonia depended, — if the application of 
ammonia be continued, and no restitution be made to the 
soil of the mineral elements removed, — then the yield must 
necessarily diminish, in the years following, in the same 
proportion as it was higher in the first and second years. 

In one word — ammonia is a most useful manure when it 
is accompanied by the mineral elements which render it 
active, or when it finds in the soil those conditions which 
are necessary to its efficacy ; it is absolutely of no value to 
the farmer if he neglect to restore or supply these elements. 

In a soil sufficiently rich in nitrogen, but poor in certain 
mineral elements indispensable to the growth of many 
plants, the application of ammonia, or of its salts, is at 
any rate useless, and often absolutely injurious. In such 
a soil, which simply is deficient in a proper supply of phos- 
phoric acid, a dose of that substance, unaccompanied by 
ammonia, will produce the same fertilising effect as guano, 
only, probably, in a higher degree. The General Commit- 
tee of the Agricultural Society of Bavaria, at Schleissheim, 
caused a portion of one of the poorest worn-out fields in the 
vicinity of Munich to be manured, by way of experiment, 
with acid phosphate of lime (phosphorite) ; the result was, 
a crop of summer wheat double in amount to that yielded 
by an equal portion of the same field unmanured. Had 
guano been the manure used in this case, the crop would 
most indubitably have far exceeded that reaped from the 
unmanured plot, and a supporter of the so-called nitrogen 
theory would as unquestionably have ascribed the effect to 



THEORETICAL AND PRACTICAL AGRICULTURE. 169 

the ammonia contained in the guano, which could not pos- 
sibly have had anything to do with it, in the foregoing 
experiment. The same manure, viz., acid phosphate of 
lime, has been applied with equal success elsewhere, with 
out any co-operation of ammonia, and frequently larger 
crops of grain have been obtained than from the use of 
guano ; it is, therefore, quite evident, that for a field in that 
condition ammonia is almost quite valueless. The expla- 
nation also of this fact has been ascertained by chemical 
examination: it has been found that most fields contain, 
within a depth of from ten to twelve inches, a hundred, 
five hundred, often even a thousand times more ammonia 
in a similar form, than is present in rotten farm-yard 
manure, in bones, or rape-dust ; it is, then, quite clear, that 
where the soil happens to be deficient in even one of the 
indispensable mineral elements of food, the existing great 
store of ammonia will be of no avail in increasing the pro- 
ductiveness of the land. 

In the vicinity of Magdeburg, the residue left after the 
distillation of beetroot-molasses, which contains the soluble 
salts of the beetroot, (no salts of ammonia) has, of late, been 
used as a manure, and I have been assured that fields 
treated with it have yielded, several years in succession, 
most abundant crops of rape, beet, &c. 

For each field there exists some effective agent of this 
kind ; but it will never be found, if we rest contented with 
simply chanting the praises of ammonia. As we have seen, 
in Letter II., the soil never contains free ammonia ; and in 
the rotten farm-yard manure the greater proportion of the 
liberated ammonia enters into chemical combination with 
the humus-constituents of the dung — being taken up by 
them directly from the liquid portion, which accounts for 
the fact that the latter is comparatively so poor in that 
ingredient. 

8 



170 THEORETICAL AND PEACTICAL AGRICULTURE. 

Free ammonia, or an ammoniacal salt, put upon a field, 
immediately forms with the constituents of the surface soil 
a combination from which the plant subsequently derives 
this element of food. In this way, the ammonia conveyed 
to the soil in rain goes on accumulating ; it would, there- 
fore, be an act of common sense to expend no money in 
the purchase of this dearest of all manuring agents, before 
first making sure that phosphate of lime, either alone, or in 
conjunction with sulphuric acid, or ash, or the two together, 
or lime, has failed to stimulate the productiveness of the 
field, in the first place, for underground plants (turnips, 
potatoes, &c.), and for the subsequent crop of cereals. It 
is only after making such trials, that the employment of 
ammonia can be justified. 

Let it not be thought, however, that the notion of the 
professors and advocates of the so-called nitrogen theory, 
which makes the nitrogen, or the ammonia, the principal 
agent in manures, and the pivot upon which all agricultural 
production turns, is purely imaginary and absolutely base- 
less. This notion has, on the contrary, arisen from a very 
pardonable error, formerly but too common in science, and 
which is still occasionally met with at the present day. 

It is quite true that the agricultural value, for the produc- 
tion of grain, of the various sorts of guano, and of all excre- 
me7its of animals, may be accurately determined by the 
proportion of nitrogen or ammonia contained in them. 
The mistake made in the matter essentially lies in this, 
that, taking their stand upon these facts, which are per- 
fectly true in themselves, people attributed the action of 
these manures to the nitrogen, which, indeed, performs a 
part in this action, but, in most cases, only a suboidinate 
one. This is the same error which Lavoisier and Davy 
committed in designating, the one, oxygen, the other, 
hydrogen, as the acid-generating principle. 



THEOEETICAL AND PRACTICAL AGRICULTURE. 171 

To compreliend this fact, we must bear in mind tlie com- 
position of grain, of flesh, and of those constituent parts of 
plants which serve to form blood, and which have a com 
position similar to that of flesh. All these matters contain 
the combustible and incombustible constituents of the 
blood. A person living on bread receives into his organ- 
ism the ash-constituents of the grain which has furnished 
the flour for the bread; his excrements contain the ash- 
constituents of the same grain. Out of the elements of the 
bread flesh is made, and the excrements of men or animals 
living on flesh are in their elements identical with those of 
men or animals living on bread or seeds. Bread, flesh, and 
blood, contain an ingredient rich in nitrogen, which, taken 
in the food, serves to sustain the vital functions, or the 
change of matter in the body : the nitrogen of this ingre- 
dient is again every day eliminated in the urine and fceces, 
in the same quantity in which it has been partaken of in 
the food. 

The excrements of men and of animals, therefore, not 
only contain the ash-constituents of the seeds, the flesh and 
the component parts of the roots, tubers, herbs, &c., that 
have served to form blood and flesh in the animal organ- 
ism, but they also contain the far greater proportion of the 
nitrogen of these seeds, and of the blood and flesh- forming 
elements. As we have already had occasion to observe, it 
has been demonstrated by the most accurate chemical 
analysis,* that there is a fixed and invariable ratio between 
the amount of nitrogen in seeds and the quantity of phos- 
phoric acid or of phosphates contained in them (between 
the nitrogen and the ash-constituents of the seed) ; so that, 
if we know the proportion of nitrogen in seeds, we can, 

* See "Results of agricultural and chemico-agricultural experiments con- 
ducted by the Greneral Committee of the Agricultural Society of Bavaria at 
Munich; Cotta's Literary and Art Institution, 1857." 



172 THEOKETICAL AND PRACTICAL AGRICULTURE. 

from this, calculate the amount of phosphoric acid, or of 
phosphates, present in them. 

Kow, in the solid and liquid excrements, these several 
constituents are naturally contained in the same, or very 
nearly the same, fixed relative proportions as in the seeds. 
The solid and fluid excrements together contain the nitro- 
gen and the ash-constituents of the bread, flesh, &c. of the 
consumed food ; and we can therefore readily understand 
how we might, by ascertaining the amount of nitrogen in 
an excrement, estimate, in an analogous way, in a tolerably 
exact manner, the quantity of mineral constituents of seeds 
or of flesh present in it. 

In point of fact, the original relative proportion between 
the nitrogen and the ash-constituents in excrements is 
altered. The nitrogen is converted in the putrefactive 
process into ammonia, a portion of which is lost by evapo- 
ration ; and even before the process of decomposition has 
set in, part of the nitrogen present is carried off*, together 
with the most efficacious soluble salts, in the liquids which 
ooze awa}^ This latter loss, however, might be guarded 
against, and ought to be so, by the use of absorbing earths. 
The proportion of nitrogen in the contents of latrines, or in 
poudrette, in farm -yard manure, and in guano, affords, 
therefore, no proper standard of their agricultural value, 
which depends upon the ash-constituents of seeds contained 
in them ; but of two sorts of guano analysed, we can, with 
tolerable certainty, regard that one as the purest in which 
is found the largest per centage of ammonia ; any adulte- 
ration of the article lessens that proportion. The same 
remark applies to poudrette which very often contains as 
much as fiff;y per cent, of sand (sweepings) and other 
extraneous matter unfit for the nutrition of plants ; and 
probably, also, this holds good for farm-yard manure. 

It is therefore by no means absurd, but quite correct, to 



THEORETICAL AND PRACTICAL AGRICULTURE. 173 

say, that tlie value of the several sorts of guano, of pou- 
drette, and of farm-yard manure, bears a certain relation to 
their amount of nitrogen. But the inference drawn from 
this fact, that the agricultural value of these manures, and 
their beneficial action upon the soil, are entirely dependent 
upon this relative proportion of nitrogen, and that, accord- 
ingly, ammonia and its salts might be used with equal suc- 
cess in cultivation, in lieu of them, is over-hasty, and 
entirely devoid of all foundation. Were a farmer, by the 
advice of the apostles of this so-called nitrogen theory, mad 
enough to manure his fields, even for ten years only, con- 
secutively with salts of ammonia, or with Chili-saltpetre, 
and were he, confidently relying upon the perfect fitness 
of these salts to replace farm-yard manure, poudrette, and 
guano, to sell off from his fields the entire produce, he 
would assuredly be a beggar at the end of this period. If 
all agriculturists in Germany were to agree never to return 
to their fields the mineral constituents of their manure- 
heaps, because their teachers have assured them that the 
soil is inexhaustible in these elements, half the population 
of Germany would be starved to death before the end of 
ten years. 

It is, altogether, one of the most discouraging signs in 
agriculture, that frequently the best-informed men will, in 
judging of the value of a manure, and of its effect, act as 
if they were devoid of judgment and common sense. 

In comparing the action of guano, bone-earth, and Chili- 
saltpetre, it will not do to draw a line under the calculation 
at the time of harvest, or after the expiration of a year, 
and argue that guano or Chili-saltpetre is a better manure 
than bone-earth, because so many more pounds of corn have 
been yielded by the use of the former than by tlie latter. 
Common sense tells us that the effect of individual manures 
must he judged ofhy the condition in which they leave the field. 



174 THEORETICAL AND PRACTICAL AGRICULTURE. 

It is very evident that if after a large crop which, has 
been obtained bj the use of Chili-saltpetre in one year, the 
soil has required in the following year a double quantity 
of manure to yield the same amount of produce, much 
money has in such a case been laid out to no purpose ; and 
I greatly fear, if an exact reckoning be kept of the produce 
of their fields for a series of years, and also of the expendi- 
ture of manure, in addition to Chili-saltpetre, agriculturists 
will find that for the money spent in the latter agent, they 
have received scarcely any other return than a very beau- 
tiful deep green colour of their crops in the first period of 
their vegetation. 

A comparison of the action of guano with Chili-saltpetre, 
and bone-earth (or phosphorite), can be made only after 
several years. If guano applied to a plot of land very per- 
ceptibly increases the potato crop in the second, and the 
clover crop in the fourth year, whilst a dose of Chili-salt- 
petre of the same pecuniary value is not followed by a 
similar increase, those after-effects must be taken into ac- 
count if we would avoid drawing a superficial estimate of 
the value of the two substances. 

When the agriculturist who makes comparative experi- 
ments with guano and other manures, and appears to have 
obtained in the first year from the guano the most favour- 
able results, points to its greater proportion of nitrogen and 
draws the conclusion that these greater effects have been 
directly due to this element, we may well ask him why he 
has not also made a comparative experiment, upon an equal 
piece of land, with a similar quantity of ammonia to that 
which is contained in guano, and in this way obtained 
a standard by which to measure the effect of ammonia in 
guano. 

But a proceeding of this kind has never yet been thought 
of by any one of these experimenters, who also keep from 



THEORETICAL AND PRACTICAL AGRICULTURE. 175 

the farmer the fact proved by the most extended and accu- 
rate experiments of Lawes, Kuhlmann, and others, that a 
pound of ammonia in guano produces five times the effect of 
the same quantity applied in the form of a salt of ammonia. 
(The action of pure ammonia is altogether unknown.) 
Now it is quite clear that the more powerful effect of the 
ammonia in the guano is simply owing to the presence and 
co-operation of other matters ; and when the combined 
action of these latter and the ammonia is found to be four 
times greater than that of the ammonia alone, then wher- 
ever it is thought desirable or requisite to use ammonia it 
will evidently be a wise step to provide for the presence of 
these matters, that in such cases likewise the action of the 
ammonia may be increased five-fold. 

When an agricultural chemist (Dr. Stockhardt) asserts 
that ''he chiefly owes to guano his positive conviction of 
the great importance of nitrogen compounds that are easily 
assimilated, and is thus indirectly indebted to it for the 
most glorious acquisitions achieved by his labours in the 
field of agricultural chemistry," the latter alone is true thus 
far, viz. that if it had not been for guano the world would 
scarcely have heard of the labour of this individual in the 
field of agricultural chemistry. A man of science ought 
not to cling to a cork buoy to enable him to swim ; and 
if it keeps him afloat he ought to be grateful for this, but 
not proud of it. Guano requires no cork buoy ; it would 
assuredly have made its way iis railways have done, as indeed 
it has done in other countries to a much greater extent than 
with us, without requiring the least aid at the hands of the 
chemist. Things which bring in money will always make 
their own way. 

When agricultural chemists maintain that ammonia or 
its salts are the universal means for the growth of wheat, 
or acid phosphate of lime for that of the turnip tribe — they 



176 THEORETICAL AND PRACTICAL AGRICULTURE. 

simply show thereby that they do not understand the essen- 
tial principles of the science of agriculture. 

The corn-growing agriculturist removes from a hectare 
(2^ acres) of his wheat field, in an average crop of corn of 
2000 kilos, 701bs. of the mineral constituents of the grain ; 
of which 34 pounds consist of phosphoric acid and 21 pounds 
of potash, and he supplies these to the consumers in large 
towns. In an ox of 5501bs weight, the town receives 
1831bs of bones, containing nearly 1201bs of phosphate of 
lime ; in the flesh, hide, and other parts of the animal 151bs 
of phosphates, which are identical with the constituents of 
the seeds of rye.* 

The annual fluid and solid excrements of a million in- 
habitants of large cities (men, women, and children), weigh 
in the dry pulverulent state 45 million pounds; in which are 
contained 10,300,000 pounds of mineral substances, mostly 
ash-constituents of bread and meat (not including five mil- 
lion pounds weight of bones of the slaughtered cattle, &c., 
nor the mineral substances in the evacuation of horses, &c.). 
These human excrements alone contain 4,580,000 pounds 
of phosphates. 

This enormous drain of these matters from the land to 
towns, has been going on for centuries, and is still going on 
year after year, without any part of the mineral elements 
thus removed from the land ever being restored to it ; a 
very small proportion only is turned to account in the 
gardens and fields in the more immediate vicinity of 
towns. 



* In the city of Munich there were slaughtered in the year 1855-56, 
16,301 heads of cattle, which, at an average of five cwt, weighed 8,150,500 
lbs.; besides which there were slaughtered 66,186 calves, swine, and sheep, 
giving, at an average of 70 lbs. each, 5,675,020 lbs. — not reckoning the cattle 
slaughtered, at the free butcheries, by the keepers of taverns and eating- 
houses. 



THEORETICAL AND PRACTICAL AGRICULTURE. 177 

It is perfectly absurd to suppose that the loss of these 
matters which are so essential to the productiveness of a 
soil should have had no influence upon the amount of its 
produce. Indeed, even the most prejudiced agriculturist 
cannot help feeling some alarm at the enormous extent of 
the loss, if he reflects upon the amazing increase in the 
yield of corn and flesh which has taken place since farm- 
ers began, by the use of guano, to restore to the despoiled 
fields only a very small fraction of the corn and flesh con- 
stituents carried away from them. I have already remarked 
upon the identity of the constituent elements of guano with 
those of human excrements. In a series of very instructive 
experiments made expressly for the purpose in six differ- 
ent parts of Saxony, it was found that a field manured with 
guano gave in three successive years for every 10 pounds 
of guano used, 15 pounds of wheat grain, 40 pounds of 
potatoes, and 28 pounds of clover more than was reaped 
from an unmanured plot of land of the same kind and 
extent. According to the condition of the field the surplus 
thus reaped varies from 10 to 20, and in England up to 22 
and even 28 pounds of corn, for every 10 pounds of 
guano used.* 

* "In the United States distances of hundreds and thousands of miles sepa- 
rate the places where the corn is grown from the markets ; the consequence 
of this may be seen in the fact that the soil is almost everywhere exhausted, 
and that the prosperity of the country is declining, instead of increasing. 

" The rate at which this decline is progressing, has lately been shown by a 
distinguished agriculturist, from whom we learn : ' That the phosphoric acid 
and the potash taken annually away from the fields, without any compensa- 
tion worth mentioning being made to them, are at the current price of the 
market worth twenty miUion dollars; that the ash-constituent of 600,000,000 
bushels of corn are annually carried away from the land without any mate- 
rial restoration of them ; that the entire annual waste of the mineral consti- 
tuents of corn is equal to 1,500,000,000 bushels of corn.' 

" To suppose, says the author of these estimates, that this state of things 
could last, and we as a nation increase in wealth, is simply ridiculous. It is 

8* 



178 THEOKETICAL AND PKACTICAL AGRICULTUEE. 

It may therefore be safely assumed that the importation 
of a million cwt. of guano is equivalent to an increased 
production of 2,000,000 cwt. of corn which could not 
have been raised by the existing stock of home-made 
manure alone ; this latter performs its own part in increas- 
ing the produce exactly the same as if the guano had not 
co-operated with it. 

only a question of time, and time will solve the problem in a way not to be 
mistaken. What we lose with our system of destroying the soil, and wast- 
ing its resources, is the very essence of our existence. 

" Our land has not yet grown feeble from this loss of its life-blood ; but the 
hour is indicated when, should the present system be persisted in, the last 
throb of the heart of the nation will cease, — when America, Greece, and 
Rome will stand side by side amidst the ruins of the past. 

" The national economic question is not how much we are able to produce, 
but how much of our annual produce is returned to the soil. Labour spent 
in the spoliation of the soil is worse tlian labour thrown away. In the latter 
case the loss falls upon the present generation, in the former, poverty is the 
inheritance of posterity. 

" Extravagance, Mr. President, is a crime which finds its punishment in 
the natural, moral, and political decay to which I have invited your atten- 
tion. Its eftects may be seen in the fact that in New York, where the ave- 
rage yield of wheat was from 25 to 30 bushels 80 years ago, it is now only 
12 bushels; Indian Corn gives only 25 bushels. In Ohio, a State which 80 
years ago was still a wilderness, the average yield of wheat is under 12 
bushels, and is decreasing instead of increasing. In Virginia there is an 
extensive tract of land, once the richest in the State, which now produces 
only an average yield of wheat of less than seven bushels ; whilst in North 
Carolina land is cultivated which produces little more than the same yield of 
Indian corn. 

" In Virginia and Kentucky tobacco was grown until the soil was com- 
pletely exhausted, and had to be abandoned ; and in the cotton districts we 
meet with a state of exhaustion unexampled in the world, for the shortness 
of the time in which it has been brought about. The growers of cotton and 
tobacco live upon their capital ; in the produce of their fields they sell their 
fruitful soil at so low a price, that for every dollar they receive they destroy 
to the value of five dollars." 

(Letters to the President on the Foreign and Domestic Policy of the Union, 
and the effects as exhibited in the condition of the people and the State. By 
H.C.Carey. Philadelphia. J. B. Lippmcott & Co. 1858. Tenth letter, p. 54.) 



THEORETICAL AND PRACTICAL AGRICULTURE. 179 

In tlie flesh and the produce of the field we have for 
centuries supplied to the large towns the constituent ele- 
ments of guano, and have never brought this guano back 
again ; and we now send vessels to Chili, Peru, and Africa 
for this substance. For every 45 million pounds of guano 
we pay the foreigner 3 million florins. By the exporta- 
tion of these elements our fields have lost in productiveness; 
were it not so, how could it have been conceivable or pos- 
sible for us to have been able to raise their fertility by the 
importation of these elements ? Where a field is truly in 
prime condition^ no manuring agent can possibly increase its 
productiveness ; the surplus yield attained by the use of 
guano is therefore usually much less on well than on ill 
managed estates. Whilst in the ease of the former it no 
longer gives a remunerative return so soon as it rises some- 
what higher in price ; the bad manager will however con- 
tinue, and justly so, to praise it as a profitable agent. 

In the year 1855-1856 above 10 million cwt. of guano 
were imported, of which the greater portion remained in 
England. In the course of half a century above 60 mil- 
lions cwt. of bones have been imported into that country ; 
yet all this mass of manure is not worth mentioning when 
considered in relation to the arable surface of Great Bri- 
tain, and is but as a drop when compared to the sea of 
human excrements carried by the rivers to the ocean. 

The loss annually sustained by the land can only be 
very partially remedied by the purchase of foreign manures. 
In the year 1852, the consumption of guano in Saxony 
amounted in the districts of Dresden, Leipzig, Zwickau and 
Bautzen to 60,000 cwt., which gives 16*9 cwt. for every 
400 acres of land ( = 55*3 hectares), or 4} pound per acre 
(3 '82 kilos per hectare). In these 3*82 kilos of guano (of 
the better sorts) there are contained not above 1^ kilo of 
the mineral constituents of seeds ; whereas there are annu- 



180 THEORETICAL AND PRACTICAL AGRICULTURE. 

ally removed from tlie fields 35 kilos per acre in the cc rn 
crop alone. If therefore Saxony imports in a year 
1,428,000 cwt. of guano containing 35 per cent, of ash- 
constituents (for about 5^ million thalers), this is no more 
than has been taken away from all the Saxon fields in a 
single corn crop. 

No more importance need be attached to these figures 
than they deserve. They are sufficiently precise to show 
that our fields would be incalculably more fertile ; that we 
might now produce infinitely more food for man upon the 
same arable area ; that we should not be forced to sacrifice 
one-half of it to cattle — if our ancestors had only prudently 
and carefully brought back from the towns and restored 
to their fields the guano carried away from them in the 
produce. 

There is not to be found among the industrial classes a 
set of men more intent upon immediate and temporary gain 
than the common peasants, and less capable of making cor- 
rect calculations in an industrial point of view ; although 
one would suspect the very reverse to be the case. 

The prudent agriculturist who purchases potatoes from 
the peasants in his neighbourhood, for the purpose of dis- 
tilling alcohol from them, or rape seed for its oil, knows 
that every two acre crop of potatoes which the peasant sells 
to him, will in the residuary matter yield him three crops 
of rye (seed), or a full crop of rape. He knows that every 
cwt. of rape in oil-cake is worth two cwt. of wheat grain to 
him ; — and in establishing a distillery or oil mill, he takes 
into due account the advantages derived from this addition 
to the conditions of the fertility of his land. 

The peasant from whom he purchases the potatoes or 
rape-seed knows that the buyer looks upon this additional 
supply of fertilising matter from the residues as important^ 
but he himself considers it of no value to his land. It never 



THEOKETICAL AND PEACTICAL AGRICULTURE. 181 

occurs to him that it would be a prudent act to retain the 
manure constituents for his own fields at the sacrifice of a 
portion of the money received for his produce. 

The seller, if he is also a farmer, should sell only the oil 
of his rape seed, and only the starch of his potatoes, — for 
in this way alone can a proper circulation be maintained. 

But the agriculturist sells not only corn, but also pota- 
toes, rape-seed, beetroot (to the sugar boiler), tobacco, hemp, 
flax, madder, poppy, and wine. 

Whilst the corn and flesh growing agriculturist exports 
m the produce of his fields only phosphoric acid, alkalies, 
and alkaline earths, he retains on the land the elements of 
the straw and of the fodder plants which pass in the rota- 
tion of his crops from one field to another. The deep root- 
ing clover and the plants of the turnip tribe take them up 
from the sub-soil, and in the form of farm-yard manure, 
continually accumulate them in the surface soil. The ma- 
nure and the surface soil receive every year an additional 
supply of soluble silicic acid, alkalies, and salts with alka- 
line bases ; but the proportion of phosphates in them is 
constantly on the decrease. 

Hence it will be readily understood why the use of these 
manuring agents — viz. soluble silicic acid, potash, and pot- 
ash salts — will not have the slightest beneficial effect on the 
fields of the corn and flesh growing agriculturist ; for his 
fields contain already an excess of these agents which 
remain inactive from the want of phosphates. We can 
further understand why the corn and flesh growing agri- 
culturist should regard in the most important light the 
supply of phosphates, of guano and of human excrements ; 
and hold the other elements of food for plants as almost of no 
value. 

On such fields, simple manuring with human excrements, 
with or without the co-operation of farm-yard manure, may 



182 THEORETICAL AND PRACTICAL AGRICULTURE. 

produce large corn crops for an infinite number of years in 
succession ; but the continued use of guano exhausts also 
this land. The excrements of man contain the full comple- 
ment of mineral elements removed in grain and flesh ; but 
in guano there is wanting a certain quantity of potash to 
replace fully these ash constituents. Hence on soils poor 
in potash (on lime and sandy soils), the action of guano after 
a certain time perceptibly diminishes, and its efiiciency is 
then restored by the addition of wood ashes, rich in potash. 

It is a very different matter with the grower of potatoes 
and beetroot, who sells his produce to the distiller or to the 
sugar maker. 

In the average produce of three hectares of land, the 
potato grower sells and takes away from the soil the grain 
constituents of four wheat crops, and upwards of 600 pounds 
of potash in addition. 

In the produce of three hectares of land the beetroot 
grower sells and takes away from the soil the grain consti- 
tuents of four wheat crops, and 10 civt. of potash besides. 
The single sugar manufactory at Waghausel supplies to 
commerce every year 200,000 pounds of salts of potash 
obtained from the residue of the molasses, and which were 
originally derived from the beetroot fields of Baden. 

It is evident that, in the cultivation of potatoes and 
beetroot, two causes of exhaustion operate on the fields : 
these kinds of produce withdraw from the soil at each 
harvest, one-third more phosphates than a wheat crop, and 
in addition to these an immense amount of potash and its 
salts. Beetroot and potato fields, abounding in potash, may 
therefore have their produce augmented by simply manuring 
with guano or super-phosphate of lime ; but as guano and 
bone manure do not replace the potash removed in the 
produce, the ultimate result is, that after a certain number 
of years the land is found to be so much the more thoroughly 



THEORETICAL AND PRACTICAL AGRICULTURE. 183 

exhausted. On other potato- and beet-root fields poor in 
alkahne elements, farm-yard manure, which abounds in 
alkalies, answers better than guano. 

The growers of marketable plants are in the most unfavour- 
able position as regards the restoration of the mineral ele- 
ments annually carried off from their fields by these parts. A 
tobacco planter takes away in the tobacco leaves an immense 
amount of mineral elements (in clover-hay, for instance, not 
above 10 per cent., in tobacco leaves, from 18 to 24 per cent.). 
If he happens to be in possession of fields for green crops 
which supply him with manure for the tobacco plants, he 
is in the same position as the agriculturist who sells and 
alienates from his land the clover, turnips, &c. grown 
thereon ; that is to say, in the coarse of a few years he is 
sure to reach a point when his land will no longer produce 
tobacco ; and driven to procure elsewhere a supply of the 
indispensable mineral elements, he now turns to his grain 
and flesh producing neighbours, and purchases from them 
at high prices their clover and turnijos in the shape of farm- 
yard manure. Now, if this neighbour, over estimating the 
quantity of farm-yard manure in his possession, disposes of 
a portion of it to the tobacco grower, he generallj^ soon 
perceives his error, by the diminution of his crops. He is 
first of all made aware that manure cannot be produced at 
will, and that the counsel given to him to " grow more pro- 
vender for his cattle, as corn crops will then be sure to fol- 
low in due course," is of no use to him ; he finds that it 
was his manure that for seven or perhaps ten harvests has 
given him the sixth or seventh grain which constituted his 
entire profit, and that in parting with his manure he has 
. actually sold for a song his profits for many years to come. 
Made wise by experience, he now sells no more farm-yard 
manure. 

The tobacco planter, finding he can no longer procure 



184 THEORETICAL AND PRACTICAL AGRICULTURE. 

manure from his neighbour, now applies to grain and flesh 
producers living farther off, who have yet to find out by 
experience what the neighbour has already discovered; 
and thus the sphere of his foraging operations in search of 
manure grows wider and wider every year, until he finds 
himself ultimately constrained to procure his manure from 
towns, and to supply by other means the elements in which 
the town manure is deficient. 

The same state of matters we find also in countries where 
the vine is extensively cultivated. Vineyards are generally 
planted on slopes, and are destitute of arable surface soil ; 
the soil is, comparatively speaking, infinitely poorer in the 
elements of food for plants, than is the case with fields 
situated in plains. Vineyards produce no manure; the 
wanting mineral elements of food are supplied, within cer- 
tain limits, from the neighbouring corn and pasture-fields ; 
and the proprietors of these, if they have an opportunity, 
in their turn pillage the neighbouring woods. 

By deep digging the vine-dresser seeks to fit his poor 
soil for the reception of the deep-rooting vine ; and by the 
occasional cultivation of lucerne and clover, he endeavours 
to accumulate by their means in the surface soil, the 
mineral elements in which it is deficient. He conveys to 
his vineyard arable soil from fields which he has acquired 
for that special purpose, and also applies as manure the 
debris of disintegrated rocks abounding in alkaline matter. 

The culture of the vine exercises accordingly on the pro- 
duction of grain and flesh an adverse influence similar to 
that caused by the planting of tobacco and other produce 
grown for sale. 

The producer of corn and flesh, according to the prevail- 
ing system, robs his own land ; the producer of wine and 
marketable plants despoils in his turn the corn and flesh 
producer; and lastly, large towns, like bottomless pits 



THEORETICAL AND PRACTICAL AGRICULTURE. 185 

gradually swallow up tlie conditions of fertility of the 
greatest countries. 

In this way the vine growers and tobacco planters of the 
Palatinate and of the Bergstrasse exhausted the fields of 
the Hessian and Badish Odenwald, and completed the ruin 
of the already impoverished and encumbered peasant who 
could not resist the tempting sound of the silver offered 
him for his manure. 

In the same way the sewers of the immense metropolis 
of the Ancient World, engulfed in the course of centuries, 
the prosperity of the Eoman peasant ; and when the fields 
of the latter would no longer yield the means of feeding 
her population, these same sewers devoured the wealth of 
Sicily, Sardinia, and the fertile lands on the coast of Africa. 

The fertility of the land has remained unimpaired for 
centuries, in such parts only where an agricultural popula- 
tion dwells crowded together on a comparatively small 
area, and where the tradesman and craftsman inhabiting 
the small towns thinly scattered over that area, till their 
own little plots of ground with the assistance of their jour- 
neymen. 

When there are living on a (German) square mile of land 
in that position, 2000 to 3000 people, no exportation of 
grain or flesh is possible, for the produce of the fields is 
only just sufficient to feed the population; a surplus for 
exportation either never or very seldom exists. The fer- 
tility of such a tract of land is kept up unimpaired by the 
regular circulation of the conditions on which this fertility 
depends. All the mineral constituents of the produce con- 
sumed are brought back without diminution to the fields 
from which they were taken. None of these elements are 
ever lost; for everybody knows the inevitable consequences, 
and is therefore careful to do his best to collect and preserve 
them. 



186 THEORETICAL AND PEACTICAL AGRICULTUEE. 

Now, supposing this same land falls into tlie hands of 
ten great proprietors, the pillage and plunder system then 
takes the place of the system of restitution and compensa- 
tion. The petty proprietor almost entirely restores to the 
field what he takes from it ; the large proprietor, on the 
other hand, sends his grain and flesh for sale to the great 
centres of consumption, and accordingly loses the conditions 
for their reproduction. After a number of years the land 
placed in this position will be turned into a desert waste 
like the Koman Campagna. 

This is the natural cause of the impoverishment of lands 
by cultivation ; there is no other ; the teachers of modern 
agriculture alone do not recognise this cause, and are with 
all their power intent upon accelerating the ruin of Ger- 
man agriculture, and making it irretrievable. Fertile fields 
■ — so these teachers tell us — are inexhaustible in the con- 
ditions of fertility ; they only require the whip to stimu- 
late them into action. Good fortune kindly sent guano to 
rescue them in their utmost need, — the result of their own 
teaching; but in their fatal hands this blessing is actually 
turned into an instrument for impoverishing the land in 
the course of time still more completely. But guano will 
ultimately also come to an end, and what is to be done 
then? 

"We have not yet come to that pass," we hear those 
exclaim, whose fields are still fertile and yield abundant 
crops; "we are not yet come to that pass," said also a 
certain robber who was admonished to lead a better life, 
until one fine morning he found the hangman's rope around 
his neck. "To that pass" it will also assuredly come at 
last with agriculturists. Their system may -be based on 
agricultural experience, but it is certainly devoid of all 
foundation in science. 



LETTER XII. 

Modern Agriculture has no history — The reason of this — Tlie history of 
Roman Agriculture shows the existence of the spoliation system at that 
period — The works of Cato, Virgil, Yarro, and Pliny inculcate, two thou- 
sand years ago, the same precepts that are now taught by many teachers 
of agriculture — Quotations from these writers, to show their opinions on 
tlie exhaustion of the ground; on the different kinds of soils, and the 
modes of improving them; on the selection of plants for the soils which 
are suitable for them ; on fallowing ; on the cultivation of green crops for 
manures ; on the different kinds of manure and their relative values, and 
modes of managing them — The various precepts inculcated of old only 
hastened the ruin of Roman agriculture. 

The history of mankind, says Timer ^ is also tlie liistory 
of agriculture. No saying can be further from the truth 
than this. All our departments of industry having any 
connection with the natural sciences have a history: 
modern agriculture alone, has none; for it is a thing of 
to-day, or, at the most, but of yesterday. What occurred 
a week ago, it knows not ; and if it is acquainted with it, 
such knowledge does not make the agriculturist any wiser. 

Facts by the million cannot be bequeathed ; but scientific 
principles which are expressions for these facts, may be so, 
because they are immutable in their nature. 

Agriculture is, of all industrial pursuits, the richest in 
facts^ and the poorest in their comprehension. Facts are 
like grains of sand which are moved by the wind, but 
principles are these same grains cemented into rocks. A 
fact simply tells us of its existence, but experience ought to 
inform us why it exists. 

Science is conservative in her nature, not destructive. 
She does not reject the truths discovered by practice, but 



188 THEORETICAL AND PRACTICAL AGRICULTURE. 

receives them ; tliej are never disputed by lier, but are 
examined and receive from her their proper import and 
further application. Science, therefore, can produce no 
revolution in practice ; but she leads the way to a series of 
progressive developments, which are evolved in natural 
sequence from each other. 

Modern agriculture has methods and working systems, 
but it is altogether deficient in fixed principles and positive 
knowledge. After so many thousand years, even our hest- 
informed and most experienced agriculturists do not yet 
hnow what kind of manure will answer best, or under what 
circumstances /resA manure ought to be used in preference 
to old, or vice versa! 

Modern agriculture has, up to this time, no connection 
with the history of the development of man ; that history 
is the mirror which reflects not only his errors and failures, 
but also his onward progress. But modern agriculture 
rejects the idea of ever being in error, and therefore she 
knows nothing oi p)^ogress. 

If the history of the development and progress of the 
human race really found a place in the study of modern 
agriculture, or if teachers of that pursuit would only take 
the trouble to make themselves acquainted with the pages 
of that histor}^, our agriculturists would know that, two 
thousand years ago, the most enlightened and most eminent 
men of ancient Eome already found the cultivation of the 
soil beset by the same difiiculties which threaten it to-day ; 
and that the same S3^stem of "high flirming" which our 
modern teachers now recommend as the best, was then 
tried, and found wanting. 

The following statements, taken from the writings of 
Columella, Cato, Yirgil, Yarro, and Pliny, are calculated to 
enlighten the agriculturist as to the actual point of " pro- 
gress" to which he has attained in the practice of his pur 



THEORETICAL AND PRACTICAL AGRICULTURE. 189 

suit ; and to show him that his modern teacher, after all, 
inculcates nothing that was not known to the world equally 
well, and often even much better, two thousand years ago. 
Eeading the twelve books of Columella, after a perusal of 
our modern manuals of practical agriculture, is just like 
stepping from an arid and barren desert into a beautiful 
garden — so fresh and charming does everything appear. 

In his preface addressed to Publius Silvinus, Columella 
says : "The Magnates of the state are in the habit of com- 
plaining of the sterility of the land, or of the unsettled state 
of the weather, which has now for a long time exerted an 
unfavourable influence on the growth of agricultural pro- 
duce ; others are of opinion that the soil has been exhausted 
by the over-productiveness of former years. But," he con- 
tinues, " no one gifted with common sense, will ever permit 
liimself to be persuaded that our earth has grown old, as 
man grows old. The sterility of our fields is to be imputed 
to our own doings, because we hand over the cultivation 
of them to the unreasoning management of ignorant and 
unskilful slaves. 

" The agriculturist requires one kind of knowledge, the 
herdsman another. The former ought to know what pro- 
duce will answer best for his land ; the latter must under- 
stand the most remunerative way of breeding cattle. Now, 
as the two pursuits are most intimately connected with 
each other, inasmuch as it is much more advantageous to 
use the provender grown on the field for home consump- 
tion, than to sell it ; and as manuring mainly contributes 
to make a field fertile, and cattle are principally kept for 
the production of manure, therefore every body who owns 
a farm must not only possess a knowledge of agriculture, 
but also of pasturage, and of the process of stall-feeding." 
—(Columella.) 

" Wherein does a good system of agriculture consist? In 



190 THEORETICAL AND PRACTICAL AGRICULTURE. 

the first place, in thorough ploughing; in the second 
place, in thorough ploughing; and, in the third place, in 
manuring." — (Cato). 

" Colour is no reliable sign of the good quality of a soil. 
For as the strongest cattle exhibit an almost infinite variety 
of colour, so is also the best land of many and divers 
colours." — (Columella). 

" There are many different sorts of soil ; such as chalky, 
sandy, clayey, &c. One soil is moist, another dry, or 
moderately so; there are rich soils and poor soils, light 
soils and heavy soils. By the intermixture of these an 
infinite variety is created. A stiff" clay soil may be 
improved by the addition of sand or marl ; a sandy soil, 
by the addition of clay." — (Pliny, Pallad. Col.) 

" Superfluous moisture must be drawn off" by ditches, 
either open or covered ; in a chalky and stiff" ground open 
ditches are preferable. Open ditches must be wider at the 
top than at the bottom; if they are of the same width 
throughout, the sides are undermined by water, and the 
falling earth fills up the ditch. Covered ditches are dug to 
the depth of three feet, half filled with small stones or 
coarse gravel, and the earth dug out is then thrown over 
the top and levelled. If neither gravel nor stones are to 
be got, then as many bundles of brushwood are thrown in 
as the narrow ditch will hold, and the whole is covered 
with earth. At the openings of the ditch, two stones are 
placed upright, as pillars, to support a third, like a small 
bridge; this keeps the ditch open." — (Col.) 

" A soil to be fertile must, above all things, be light and 
friable, and this condition we seek to bring about by the 
operation of ploughing." — (Yirgil). 

" Ploughing the land simply means rendering the earth 
porous and friable, which most tends to increase its produc- 
tiveness." — (Cato.) 



THEORETICAL AND PRACTICAL AGRICULTURE. 191 

" The ancient Komans held, that a field which required 
harrowing could not have been well ploughed." — (Colu- 
mella.) 

" A heavy soil should be turned up in autumn, and 
ploughed three times, and the furrows be multiplied and 
drawn so closely together, that it may be barely possible to 
distinguish from which side the plough has proceeded; 
for by these means weeds are thoroughly rooted out. 
Fallow land must be ploughed until it is almost reduced to 
powder. The owner of a farm should often ascertain for 
himself whether it is properly ploughed. For this purpose, 
he need simply thrust a staff through the furrows (the 
Eomans laid out their fields in broad undulating ridges, as 
may still be seen at the present day in the neighbourhood of 
Nuremberg ; only the Koman ridges were much broader) ; 
if the staff passes through unresisted, it is a sure sign that 
the soil has been properly ploughed. Care must be taken 
to break clods of earth. Fields should be ploughed when 
neither too dry nor too wet ; if the soil is too hard, the 
plough will not penetrate, or it will simply tear off large 
clods. Even the best soil is unfruitful in its deeper layers, 
and the large lumps of earth torn up by the plough bring 
part of this subsoil to the top, which tends to deteriorate 
the arable surface soil. Always select for your fields those 
plants that may be best suited to their positions " (Cato) ; 
*' for all plants will not thrive equally well in all sorts of 
soils." — (Yarro). '' Some plants require a dry soil, others 
thrive best in moist ground." — (Col.) "Katurally moist 
ground answers best for pasturage." — (Cato). " Hay grown 
on naturally moist ground is better than where its produc- 
tion has to be stimulated by irrigation. A meadow plot in 
a plain must have a slight fall, that rain and other water 
may not gather on it in pools, but gently flow off." — 
(CoL). The seeds intended for sowing should be picked 



192 THEORETICAL AND PRACTICAL AGRICULTURE. 

out bj hand, and pulse be previously soaked in saltpetre 
water : — 

" Still will the seeds, tho' chos'n with toilsome pains 
Degenerate, if man's industrious hand 
Cull not each year the largest and the best. 
'Tis thus by destiny, all things decay 
And retrograde, with motion unperceived." 

Kennedy's YirgiVs Georg. 

" Take care to bave your corn weeded twice with the boe, 
and also by band." — (Cato). 

" On large estates fields are alternately allowed to lie fal- 
low in order to save manure." — (Pliny). " Where want of 
space forbids this, green crops are grown alternately with 
cereals, and the loss of productive energy is restored by 
manuring." — (Cato, Columella). ^' Some agriculturists grow 
cereals on their fields two years in succession ; proprietors, 
however, forbid this to their tenants." — (Festus). " The land 
must rest every second year, or be sown with lighter kinds 
of seeds, which prove less exhausting to the soil." — (Yarro). 

" Of the leguminous plants, lupines first deserve our 
attention, because they require the least labour, are cheap- 
est, and of all seeds are the most profitable for the land ; 
they give the best manure for impoverished fields, and will 
grow on a sterile soil. 

" Some of the leguminous plants manure the soil according 
to Saserna, and make it fruitful, whilst others exhaust it, and 
make it barren. Lupines, beans, peas, lentils, vetches are 
reported to manure the land. Of lupines and vetches I 
believe this to be truly the case, provided they be cut down 
green, and ploughed in before they are dry." — (Columella). 
"Linseed, poppy, and oats exhaust the soil." — (Virgil). 
" For fields that have suffered from the cultivation of these 
plants, manuring is the only efficacious means by which the 



THEOKETICAL AND PRACTICAL AGRICULTURE. 193 

lost productive energy of the earth is restored." — (Columella). 
" There are three kinds of manure: the best is the excrement 
of birds ; then comes that of man ; and lastly, that of cattle. 
The last also varies in quality. Asses' dung is the best ; 
then follow sheep's dung, and that of goats, horses, and 
cattle; the least efficacious of all is the dung of swine. 
Where an estate consists altogether of corn-fields, there is 
no need to put on every kind of manure separately; but 
where there are plantations of trees, arable land, and pas- 
turage, every kind of manure should be applied separately." 
— (Columella). " Pigeons' dung (guano) should be spread 
on meadows and gardens, or over the seeds." — Cato, Yarro, 
Cassius). " Horse-dung is about the best suited for meadow 
land, and so in general is that of beasts of burthen fed on 
barley; for manure produced from this cereal makes the 
grass grow luxuriantly." — (Yarro). 

'' Ash also is used with advantage on fields ; and on the 
other side of the Po," says Pliny, "the use of ash is viewed 
so favourably by farmers, that they actually prefer it to the 
manure furnished by their cattle. Should there be no kind 
of manure at hand, the example of my paternal uncle, M. 
Columella, may be followed with advantage ; he would not 
manure his vineyard, as he was of opinion that this tended to 
impair the fine flavour of the wine ; but he applied a layer of 
artificial mould, or earth brought from the woods, and made 
sure of obtaining by this means a more abundant vintage. 
Where no kind of manure is to be had, I think the cultiva- 
tion of lupines will be found the readiest and best substitute. 
If they are sown about the middle of September in a poor 
soil, and then ploughed in, they will answer as well as the 
best manure." — (Columella). 

" Agriculturists ought to know that a field will indeed 
lose its productive power when left altogether unmanured ; 
but that, on the other hand, over-manuring is also very 

9 



194 THEORETICAL AND PRACTICAL AGRICULTURE. 

prejudicial. Let farmers, therefore, manure ulieir fields 
often, rather than over much at a time." — (Columella). 

'' I have here one more remark to add, namely ; that 
manure is best suited for the field when it is a year old. 
In summer it ought to be turned up and always kept moist, 
in order that the seeds of noxious weeds in it be rotted, and 
be not again returned to the land." — (Col.) 

" The best fodder plants are lucerne, fenugreek {Fcenum 
grcecum), and vetches. Lucerne may be placed in the 
foremost rank of such plants ; for when it is once sown, it 
lasts ten years, fattens lean cattle, and has a salutary action 
on sick cattle. It must be carefully weeded at first, lest 
the weeds choke the tender lucerne." — (Columbella). 

" A field is not sown entirely for the crop which is to be 
obtained the same year, but partly for the effect to be pro- 
duced in the following; because there are many plants 
which, when cut down and left on the land, improve the 
soil. Thus, lupines, for instance, are ploughed into a poor 
soil, in lieu of manure." — (Yarro.) " Mow your hay at the 
proper season, and take care not to be too late with it ; you 
must cut it before the seed ripens, and store the best hay 
separately." — (Cato.) " Mossy meadows may be improved 
by a fresh sowing, or by manuring ; but neither of these 
operations will answer so well as frequent strewing with 
ash, which destroys the moss." — (Columella.) 

All these rules had, as history tells us, only a temporary 
effect ; they hastened the decay of Eoman agriculture ; and 
the small farmer ultimately found that he had exhausted all 
his expedients to keep his fields fruitful, and reap remune- 
rative crops from them. Even in Columella's time, the 
produce of the land was only fourfold. The fields fell into 
the hands of the large landed proprietors, who, by employ- 
ing a multitude of slaves, were for a time enabled to obtain 
"the largest crops at the least expenditure of manure." 



THEORETICAL AND PRACTICAL AGRICULTURE. 195 

Even by these means the land was in the end not able to 
bear the heavy taxation ; and, as the history of the first 
three centuries of our era informs us, there ensued a con- 
dition of the population, the most calamitous and frightful 
into which a nation can fall. It is true that many causes 
co-operated in producing this result, but assuredly one of 
these was the exhaustion of the soil by the spoliation sys- 
tem of agriculture then pursued. 



LETTER Xin. 

The true object to be kept in view in establishing Scientific Principles — In 
scientific agriculture, "Manure," like the term '"Phlogiston," has no longer 
a meaning — The cultivation of Green Crops for the purpose of keeping a 
stock of Cattle for manure is not necessary in the cultivation of land — The 
distinction between the Necessity and the Utility of keeping cattle — No 
necessary connection exists between the production of Corn, and that of 
Flesh and Cheese — The fundamental principles of German Agriculture 
quite unknown in China — Chinese Agriculture— The manures employed 
by them — Great value set by Chinese on human excrements ; their mode 
of collecting and using them — Chinese compost — Their mode of sowing 
and transplanting wheat — Plants cultivated as green manure for rice fields 
— The lesson taught by the Chinese system of agriculture. 

I WILL show the teachers of agriculture another people, 
who, without the aid of science, of which they know 
nothing, have found the philosopher's stone, which these 
very teachers, in their blindness, vainly seek. I will point 
out to them a land, the fertility of which has for three 
thousand years never decreased, but, on the contrary, has 
been ever on the increase ; and where more men are 
crowded together on a square mile than are to be found on 
the same space in Holland or England. 

According to the testimony of all reports of our own 
and former times, made by Davis, Hedde, Fortune, and 
others, and which have been fully borne out by the 
special inquiries into the state of Chinese husbandry, insti- 
tuted on the spot at my request, by the direction of the 
late Sir Robert Peel, it appears that in China, nothing is 
known of meadow culture^ or of fodder plants^ which are 
grown for the sake of cattle. Farm-yard manure is equally 



THEORETICAL AND PRACTICAL AGRICULTURE. 197 

unknown ; every field yields produce twice a year^ and is 
never allowed to lie fallow. 

Wheat often produces one hundred and twenty fold 
and upwards (Eckeberg) ; and a fifteen-fold crop is con- 
sidered an average yield (Davis). All those means which 
the German teacher of agriculture regards as indispensable 
for increasing the produce of our fields, and instructs his 
followers to employ, are not only entirely dispensed with by 
the Chinese farmer, but he actually obtains, without their 
co-operation, crops which exceed more than two-fold those 
.of the German high farmers. 

I readily admit that the Chinese are differently circum- 
stanced from what we are in Europe. Most of them are 
Buddhists, and eat no beef; we eat more flesh, and must 
consequently grow fodder for the production of that article 
of our diet. But that is not the question before us, but one 
which concerns those principles that are to guide the prac- 
tice of husbandry. Our teachers of modern agriculture 
do not tell us to grow fodder that flesh may be produced ; 
but that we ought to do so for the purpose of forming 
manure ; which clearly shows that they have no just con- 
ception of the true nature and aim of agriculture, and that 
they are altogether ignorant of scientific principles in the 
matter. 

In laying down a scientific principle, the first point for 
consideration is not whether the application of it will turn 
out profitable or not ; but whether it is true ; for if it is a 
true principle, it must prove advantageous. 

In scientific agriculture "manure" finds no longer a 
place; for the notions that were formerly attached to the 
term are completely obsolete ; just as is the case with the 
word Phlogiston^ which, up to the end of last century, was 
used to explain chemical phenomena. 

So long as the nature of Phlogiston was unknown, that 



198 THEORETICAL AND PRACTICAL AGRICULTURE. 

word served as a collective term to connect togetler, in an 
intelligible form, a number of unknown operating causes ; 
but when it had once been settled what " Phlogiston" really 
meant and represented, the term had to give way to more 
correct ideas ; and interpretations of phenomena became 
what they had never been before, viz. real and trustworthy. 
Wood does not, on that account, burn differently now-a- 
days from what it formerly did ; the air played the same 
part in its combustion then as now ; and water still possesses 
the same property of making bodies wet ; but what immense 
progress has been made by mankind, as the result of sub- 
stituting for the word " Phlogiston," the proper conceptions 
of the nature of air, of oxygen, and of the process of com- 
bustion ! 

A similar progress, but much more important, and infi- 
nitely more beneficial to man, will spring from a correct 
apprehension of the process of nutrition in plants and 
animals. Absurd as would now be the attempt of a teacher 
of Chemistry to account for any chemical process by having 
recourse to phlogiston, it is no less inadmissible in a teacher 
of scientific agriculture to explain a given fact by attribut- 
ing it to " manure ;" for, in the place of the obsolete notion 
of " manure," which has no longer any meaning^ we have 
now for every plant certain positively known elements of 
food^ to the united action of which we have to look for an 
explanation of the fact or phenomenon in question. 

The doctrine which inculcates as necessary for the cul- 
tivation of the land, the production of manure by green 
crops, and along with this the maintenance of a stock of 
cattle, is erroneous. 

It is necessary here to distinguish between necessity and 
utility. A stock of cattle may prove very useful to the 
farmer, and yield him a remunerative return in butter, 
cheese, and meat ; but this is quite a distinct affair from the 



THEORETICAL AND PRACTICAL AGRICULTURE. 199 

tillage of his fields, and he ought to know, and must be 
taught, that there is absolutely no compulsion upon him to 
keep a stock of cattle. 

The keeping of cattle is necessary for the production of 
manure ; hut the production of manure is hy no means neces- 
sary for the fertilisation of corn fields. In the system of the 
rotation of crops, all that is required is that green crops 
should be grown, and that their constituent parts be incor- 
porated with the arable surface soil of the field ; and it is 
quite immaterial for the cereals whether the green crops be 
previously eaten by the cattle and converted into manure or 
not. 

If lupines, vetches, clover, turnips, &c., are cut up and 
ploughed in, in the green state, their action is far more 
powerful. 

There is no natural connection of mutual dependence 
between the production of corn and that of flesh and cheese ; 
on the contrary, they interfere with each other, and must 
in science be considered as perfectly distinct and separate 
things ; for the production and sale of flesh is carried on at 
the expense of grain, and vice versd. We cannot do with- 
out meat, milk, or cheese ; and if the production of these 
articles be left entirely to the grazier, who, on his part, ought 
to meddle as little as possible with the growing of grain, 
both he and the farmer, as well as the consumer, would 
profit by it. In England this separation of the two pur- 
suits is gradually gaining ground ; and when, as is to be 
hoped, our German farmer shall have succeeded, in the 
course of time, in mastering the multiplication table, we 
may expect that the same separation will take place in 
Germany. Chemical manufactories are not established any- 
where and everywhere, but only in localities offering cer- 
tain natural advantages ; and Agriculture, after all, is 
simply an industrial pursuit, like any other. 



200 THEOliETICAL AXU PKACTICAL AGRICULTUEE. 

In CHna they know nothing of the fundamental prin- 
ciples upon which German agriculture is based. Except 
green manuring, they neither know nor esteem the applica- 
tion of any kind of manure beyond the excrements of man. 
The other matters occasionally employed by them to in- 
crease their crops, are in quantity and effect utterly in- 
significant, when compared with the use of human excre- 
ments. 

It is quite impossible for us in Europe to form an ade- 
quate conception of the great care which is bestowed in 
China upon the collection of human excrements. In the 
eyes of the Chinese, these constitute the true sustenance of 
the soil (so Davis, Fortune, Hedde, and others tell us), and 
it is principally to this most energetic agent that they 
ascribe the activity and fertility of the earth. 

The Chinese, whose house is still, what it most probably 
has ever been, a tent, only that it is built of stone and 
wood, knows nothing of privies as we have them in our 
country ; but, in their stead, there are found in the princi- 
pal and most comfortable part of his dwelling, earthenware 
tubs, or cisterns most carefully constructed of stone and 
lime ; and the notion of utility so completely prevails over 
the sense of smell, that, as Fortune tells us ("The Tea Dis- 
tricts of China and India," vol. i., p. 221), " what in every 
civilised town of Europe would be regarded as a most in- 
tolerable nuisance, is there looked upon by all classes, rich 
and poor, with the utmost complacency, and," he continues, 
" nothing would cause greater surprise to a Chinese than to 
complain of the stench arising from these receptacles." 
The Chinese do not disinfect this manure ; but they are 
perfectly aware that it loses part of its fertilising power by 
the action of the air ; and they, therefore, take great care 
to guard against evaporation. 

Except the trade in grain, and in articles of food, gene- 



THEOEETICAL AND PRACTICAL AGRICULTURE. 201 

rally, there is none so extensively carried on in China as 
that in human excrements. Long clumsy boats, which 
traverse the street canals, collect these matters every day, 
and distribute them over the country. Every Coolie who 
has brought his produce to market in the morning, carries 
home at night two pails full of this manure on a bamboo 
pole. 

The estimation in which it is held is so great, that every- 
body knows the amount of excrements voided per man in 
a day, month, or year ; and a Chinese would regard as a 
gross breach of manners the departure from his house of a 
guest who neglects to let him have that advantage to which 
he deems himself justly entitled in return for his hospitality. 
The value of the excrements of five people is estimated at 
two Teu per day, which makes 2000 Cash* per annum, or 
about twenty hectolitres (440 galls.), at a price of seven 
florins. 

In the vicinity of large towns, these excrements are con- 
verted into poudrette, which is then sent to the most distant 
places, in the shape of square cakes, like bricks. For use, 
these cakes are soaked in water, and applied in the fluid 
form. With the exception of his rice fields, the Chinese 
does not manure the field, but the plant. 

Every substance derived from plants and animals is care- 
fully collected by the Chinese and converted into manure. 
Oil cakes, horn, and bones, are highly valued, and so is 
soot, and more especially ash. To give some notion of the 
value set by them upon animal ofial, it will be sufficient to 
mention that the barbers most carefully collect, and sell as 
an article of trade, the somewhat considerable amount of 
hair of the beards and heads of the hundreds of millions 
of custd mers whom they daily shave. The Chinese know 



100 Cash are equal to about 4^d. (Fortune). 



202 THEOKETICAL AND PRACTICAL AGRICULTURE. 

the action of gypsum and lime ; and it often happens that 
they renew the plastering of the kitchens, for the purpose 
of making use of the old matter for manure. — (Davis.) 

No Chinese farmer ever sows a seed of corn before it has 
been soaked in liquid manure diluted with water, and has 
begun to germinate ; and experience has taught him (so he 
asserts), that this operation not only tends to promote the 
growth and development of the plant, but also tc protect 
the seed from the insects hidden in the ground. — (Davis.) 

During the summer months, all kinds of vegetable refuse 
are mixed with turf, straw, grass, peat, weeds, and earth, 
collected into heaps, and when quite dry, set on fire ; after 
several days of slow combustion, the entire mass is converted 
into a kind of black earth. This compost is only employed 
for the manuring of seeds. When seed time arrives, one 
man makes holes in the ground ; another follows with the 
seed, which he places in the holes ; and a third adds this 
black earth. The young seed planted in this manner grows 
with such extraordinary vigour that it is thereby enabled 
to push its rootlets through the hard solid soil, and to col- 
lect its mineral constituents. — (Fortune.) 

" The Chinese farmer sows his wheat, after the grains 
have been soaked in liquid manure, quite close in seed- 
beds, and afterwards transplants it. Occasionally, also, the 
soaked grains are immediately sown in the field properly 
prepared for their reception, at an interval of four inches 
from each other. The time of transplanting is towards the 
month of December. In March the seed sends up from 
seven to nine stalks with ears, but the straw is shorter than 
with us. I have been told that wheat yields 120 fold and 
more, which amply repays the care and labour bestowed 
upon it." — (Eckeberg, Eeport to the Academy of Sciences 
at Stockholm, 1765.)* 

* The Dresden Journal, of 16th September, 1856, contains the follow- 



THEOEETICAL AND PRACTICAL AGRICULTURE. 203 

In Chusan, and the entire rice districts of Chekiang and 
Keangsoo, two plants are exclusively cultivated for tlie 
purpose of serving as green manure for the rice fields ; the 
one is a species of Coronilla, clover is the other. Broad 
furrows, similar to those intended for celery, are made, and 
the seeds are planted on the ridges in patches, at a dis- 
tance of five inches from each other. In the course of a 
few days germination begins, and long before the winter is- 
gone, the entire field is covered with a luxuriant vegeta- 
tion. In April the plants are ploughed in ; and decompo- 
sition soon begins, attended with a most disagreeable odour. 
This method is adopted in all places where rice is grown. — • 
(Fortune, vol i., p. 238). 

These extracts, which, from want of space, cannot be 
further extended, will probably suflice to convince the 
German agriculturist, that his practice, when compared 
with that of the oldest agricultural nation in the world, 
stands somewhat in the position of the acts of a child to 
those of a full grown and experienced man. The Chinese 
system of husbandry is the more remarkable, if we take 

ing statement: — "As we are informed from Eibenstock, forest-inspector 
Thiersch, of that place, has for several years past made very successful 
experiments in transplanting winter corn in the autumn. He transplanted 
the young plants intended for the purpose in the middle of the month of 
October, one peck of seed-corn to one hundred square rods of ground, which 
produced an uncommonly rich crop. There were roots from which sprung 
as many as fifty-one stalks with ears, and the latter contained as many as 
one hundred grains." 

I have applied to Mr. F. J. Thiersch for more precise details of his experi- 
ments ; and from his statement as to the cost of the operation and the 
return made, there appears to be no doubt that the Chinese mode of hus- 
bandry might also be resorted to with advantage in Europe, in locahties 
where the land is rich and labour abundant. One of my friends, who visited 
M. Thiersch's experimental field, told me that he had counted twenty-one 
stalks with full ears on a plant pulled up at hazard (not picked out). For 
poor fields this method of cultivation is entirely unsuited. 



204: THEOKETICAL AND PKACTICAL AGRICULTURE. 

into account what they have achieved in other mechanical 
and chemical pursuits, more incomprehensible, as they owe 
everything to the purest empiricism. For the Chinese 
system of instruction has, for thousands of years, so 
thoroughly excluded every inquiry after an ultimate cause 
of things, which might possibly have led to the discovery 
of scientific principles, or to the establishment of a science, 
that the capability of making further progress, except by 
imitation, would seem to be destroyed to the very root in 
that people. The study of the physical laws, which has 
led European nations to the invention of the steam-engine, 
and of the electric-telegraph, and has enabled man to con- 
trol and turn to his account the forces of nature in number- 
less other instances, is a matter of absolute impossibility to 
the Chinese scholar. It is the express command of their 
first and most ancient teacher of religion, Confucius, that 
the student shall never allow any thought to rise in his 
mind but such as he finds written in his books. 

It is quite true that what suits one people may not on 
that account suit all countries and all nations; but one 
great and incontrovertible truth may, at all events, be 
learned from Chinese agriculture, viz., that the fields of 
the Chinese cultivator have preserved their fertility unim- 
paired, and in continued vigour ever since the days of 
Abraham, and of the building of the first Pyramid in 
Egypt.* This result we also learn has been attained solely 
and simply by the restitution to the soil of the mineral con- 
stituents removed in the produce ; or what amounts to the 
same thing, that this has been effected by the aid of a ma- 
nure, of which the greater portion is lost to the land in the 
European system of cultivation. 

* Vessels of Chinese porcelain are found in the Pyramids, of the same 
shape, and with the same characters of writing on them, as are made in 
China at the present day. 



LETTEK Xiy. 

The law of Compensation is of universal application — Elementary information 
on Chemical subjects connected with Agriculture easily imparted — Im- 
portance of instructing youth at school in these fundamental truths — Theo- 
retical instructions should always precede Practical — The proper mode of 
instructing agriculturists in the Theory and Practice of Agriculture — The 
present constitution of Agricultural institutions very defective — The false 
position of Science in practical agriculture is the result of the teachings of 
these Schools — The demands made by Science on agriculturists are simple, 
and a knowledge of them cannot prove injurious — Science demands that 
agriculturists should test the Truths she advances — The truths in these 
Letters expressed by a Formula — The value of Guano first discovered by 
Science — The establishment of Reservoirs for animal excreta strongly 
recommended— Rehance to be placed upon such Excreta rather than on 
Guano — Chemistry can only help agriculturists after they have exhausted 
all the means at their disposal — Notes on supply of guano and ou the 
agriculture of Tuscany. 

The European husbandman has, for centuries past, been 
in the habit of taking away the produce of his fields, with- 
out making compensation for the mineral matters removed, 
and his fields have accordingly been continually diminish- 
ing in fertility. 

The Chinese husbandman has, for thousands of years 
past, made it a practice to restore to his fields the mineral 
constituents removed from them in the produce, and the 
fertility of his land has accordingly kept pace with the in- 
crease of the population. 

The law of compensation, which makes the recurrence 
or permanency of effects dependent upon the recurrence or 
permanency of the conditions which produce them, is the 
most universal of the laws of nature ; it governs all natural 



206 THEOKETICAL AND PKACTICAL AGRICULTUEE. 

phenomena in their various phases, all organic processes^ 
all the productions of man's industry. That the agricultu- 
rist alone should ignore this law, nay, that his teachers and 
guides should actually deny its operation, shows clearly 
the condition of the schools in which the sons of our far- 
mers are taught. 

What Chemistry teaches about air, water, the process of 
combustion, arable soil, the ash of plants, manure and its 
constituents, is so easy of comprehension, that every well- 
informed teacher may, in a dozen lessons, and with the sim- 
plest means of instruction, impart to the commonest peasant 
boy an accurate knowledge of these things ; particularly if 
the teacher strictly confine himself to his subject. The lec- 
tures occasionally delivered on matters of this nature at the 
Eoyal Institution of London, by Professor Faraday, before 
an audience of children, may be adduced in proof that it 
is quite practicable to do so. 

By command of King Maximilian, a movement in this 
direction has of late been made in Bavaria. Five years 
ago, all the teachers of the schools for training schoolmasters 
were, for this purpose, specially instructed and exercised in 
Munich. 

The diffusion of this elementary knowledge among the 
peasantry through the agency of the schoolmaster, will be 
an immense step in advance, and will prove the very best 
thing that the state can do in the interest of agriculture. 

The boy who has been taught at school, even though 
superficially, the conditions on which the fertility of the 
field depends, and who has been told by his teacher, that 
he who uselessly wastes these conditions is guilty of an 
offence against the poor, against himself, and against society, 
will certainly, when he grows up to man's estate, construct 
receptacles for human and animal excrements, such as no 
police regulations could ever compel him to provide. 



THEORETICAL AND PRACTICAL AGRICULTURE. 207 

A superficial examination of the system prevailing in tlie 
higher agricultural institutions, is sufficient to convince us, 
that, such as they are at present, they are totally unsuited 
for the requirements of our day. 

The combination of the ordinary arrangements of a 
school, with instructions in the practical work of agricul- 
ture, does away with the benefits which might be derived 
from such institutions, which are neither one thing nor an- 
other; they are neither educational institutions nor good 
practical workshops ; they possess some of the features of 
both, but none of the good points of either. 

The technical part of an industrial pursuit can be . 
learned; principles alone can be taught. To learn the trade \ \ 
of husbandry, the agriculturist must serve an apprentice- i ; 
ship to it ; to inform his mind in the principles of the I i 
science^ he must frequent a school specially devoted to this \i 
object. 

It is impossible to combine the two ; the only practicable 
way is to take them up successively. I formerly conducted 
at Griessen a school for practical chemistry, analysis, and 
other branches connected therewith, and thirty years' expe- 
rience has taught me that nothing is to be gained by the 
combination of theoretical with practical instruction. A 
student of chemistry who attends the lecture-hall and the 
laboratory concurrently, positively defeats thereby the 
object of his stay at the school, and misses the aim of his 
studies. It is only after having gone through a complete 
course of theoretical instruction in the lecture-hall that the 
student can with advantage enter upon the practical part 
of chemistry ; he must bring with him into the laboratory 
a thorough knowledge of the principles of the science, or 
he cannot possibly understand the practical operations. If 
he is ignorant of these principles, he has no business in the 
laboratory. ^ 



208 THEOKETICAL AND PRACTICAL AGRICULTURE. 

In all industrial pursuits connected with the natural 
sciences, in fact, in all pursuits not simply dependent on 
manual dexterity, the development of the intellectual facul- 
ties, by what may be termed " school learning," constitutes 
the basis and chief condition of progress and of every im- 
provement. A young man, with a mind well-stored with 
solid scientific acquirements, will, without difficulty or 
effort, master the technical part of an industrial pursuit; 
whereas, in general, an individual who may be thoroughly 
master of the technical part, is altogether incapable of seiz- 
ing upon any new fact that has not previously presented 
itself to him, or of comprehending a scientific principle 
and its application. 

I have often found that students coming from good col- 
leges will speedily leave the pupils of industrial and poly- 
technic schools far behind them even in the natural sciences^ 
though the latter, when compared with the former, were at 
first giants in knowledge. 

I am far from wishing to question in any way the very 
great utiUty of industrial and technical schools. I consider 
them just as indispensable as higher schools ; for the same 
road is not suited to all men, and every one does not pos- 
sess an aptitude for the study of languages. The minds 
of youth may be compared to a variety of ores, requiring 
different furnaces for the smelting and extraction of the 
metal, and the removal of the slags. But talent is like 
gold ; wherever it occurs in nature it is found in its pure 
state, never as an ore, and every furnace is equally suited 
to it. 

In our agricultural academies the training of the pnpils 
in the mechanical and technical branches is continually 
interfering with their proper instruction in principles and 
theories in the school. Whenever a new sowing machine, 
or a plough, or some other agricultural implement is to be 



THEOEETICAL AND PRACTICAL AGRICULTURE. 209 

tried, the lecture-halls of Chemistry, Physics, &c., are 
deserted. The greater portion of their teachers of Mathe- 
matics and the Natural Sciences have received a university 
education, and are, as may be expected, able scientific men , 
but their teachings are held of secondary importance to the 
practical work of husbandry ; they become speedily dis- 
couraged; and, under sach circumstances, a solid course of 
instruction in the natural sciences is out of the question. 
I never yet met with one pupil trained at one of these insti- 
tutions, who had a correct conception of the theory of dew, 
or who was able to distinguish the seeds of the meadow 
grasses, or the grasses themselves. 

The learning of a technical pursuit is a different thing 
from the acquirement of an art which demands practice. 
The pupil of an academy of fine arts may see from day to 
day what progress he has been making ; and this gives him 
the necessary encouragement, which again tends to stimulate 
his ardour, and makes him persevere in his efforts. But the 
pupil at an agricultural academy has no standard by which 
to measure the progress he has been making in technical 
knowledge ; the incentive to exertion is wanting, and all 
emulation ceases. 

The young agriculturist who wishes to acquire a com- 
petent knowledge, both theoretical and practical, of his pur- 
suit, ought to visit, in the first place, a university to obtain 
the necessary knowledge of the natural sciences, and after- 
wards an agricultural institute, where the principles of 
agriculture, and, at the same time, its practical operations, 
are taught on a large scale. 

Kow, if we reflect that the majority of our agricultural 
academies have, for a generation past, been conducted in a 
measure by men who have no knowledge whatever of 
Chemistry, Physics, Botany, Geognosy, &c., the conviction 
forces itself upon the mind, that they have been much more 



210 THEORETICAL AND PRACTICAL AGRICULTURE. 

schools of idleness, and of opposition to all progress, than 
institutions for advancement. 

The conflict at present raging about the principles of 
science and their application to practical husbandry, is the 
work of these schools ; and no one need wonder if the prac- 
tical man should hold science in little respect, nay, if he 
should regard it with positive contempt. For, whence can 
this estimation and regard for science proceed, except from 
a knowledge of its principles ? 

I am ready and willing to retract every word I have 
uttered against these institutions, if any one will solve, in 
some other way, the enigma which the antagonism between 
the precepts of science and the practical lessons of agriculture 
presents. The former do not simply embrace the principles 
at which a single individual has arrived ; but they com- 
prehend the general principles of all science. All chemists 
and physicists, all students of nature and mathematicians, 
entertain them, because they are simply expressions of that 
method to which they all owe their success. 

All practical men are agreed on this one point, that they 
ought not to alter their practice on account of a doctrine, 
however probable it may appear ; they demand to be first 
convinced of its truth, and then, as a matter of course, all 
opposition on their part will cease. This condition would 
be reasonable enough, were there anything in this doctrine 
which might possibly prove injurious to their interests ; but 
their opposition is not directed against the doctrine, but 
against common sense, and no science in the world can over- 
come opposition of such a nature. 

The scientific principles which chemistry wishes to in- 
troduce into agriculture are so very simple, and the 
demands made upon the practical husbandman are so much 
to his own advantage, that, to an unprejudiced person, his 
opposition is incomprehensible. 



THEOEETICAL AND PEACTICAL AGRICULTURE. 211 

Science has taken upon herself to accomplish what was 
beyond the power of practice, from its very nature, to do. 
She has thoroughly examined the soil, the air, the excre- 
ments of man and of animals, the roots and tubers of plants, 
their leaves, stalks, seeds, and fruits, the blood and flesh of 
animals ; she has, in short, investigated everything of a 
combustible and incombustible nature contained in organic 
bodies, and which is of importance in their production. 
The results of her researches and analyses she has laid 
before the practical agriculturist, and has shown him that 
plants^ manures^ and the soil^ have certain constituent ele- 
ments in common. From the constant presence of these 
constituent elements in plants, she has inferred that they 
are indispensable to the formation of the plant and its parts 
— an inference which naturally leads to the conclusion that 
they are equally necessary in the soil in which the plants 
are to grow, as well as in the manure which is intended to 
aid their growth. Science has also demonstrated, still with 
the balance in her hands, that even a soil regarded as 
abounding in these constituent elements contains in reality 
only a comparatively very small proportion of them. 

Science demands from the practical agriculturist no more 
than that he should acquire the very trifling amount of 
chemical information requisite to enable him to understand 
the language of chemistry, and to test the correctness of 
these facts. It would be absurd in the extreme to fancy 
that this could in any way tend to interfere injuriously 
with the practical operations of husbandry. She asks the 
farmer to test the correctness of these facts in his own way ; 
to prove by actual experiment, whether a field which does 
not possess these constituent elements, is nevertheless a 
fruitful soil for the production of cultivated plants ; and if 
not, whether it may be made fruitful by a proper supply of 
these matters. She asks him further to try if a field 



212 THEORETICAL AND PRACTICAL AGRICULTCJRE. 

abounding in these elements is rendered barren by their 
removal ffom it. Surely a trial of this kind cannot be said 
to be of a nature likely to interfere injuriously with the 
practical operations of husbandry. 

When agriculturists have in this way acquired the con- 
viction that the facts and inferences of chemistry agree 
with the facts and results of the agricultural test applied, 
everything has then been done that can be done by chemistry 
for agriculture. The instructions given beyond this no 
longer pertain exclusively to the domain of chemistry, but 
are common to all sciences. 

When, therefore, the agriculturist has, in the* manner 
just described, ascertained that the facts and inferences 
advanced by chemistry are fully borne out by the results 
of agricultural experience, it can surely only be to his own 
advantage to shape his practice by her lessons, and to make 
the necessary changes in those portions of his operations 
which he finds have been founded in error. It is not che- 
mistry alone, but common sense, and everything besides 
connected with these facts, which require him to do this. 
Common sense tells him that he ought to provide for his 
fields a proper supply of these constituent elements, and 
restore them where they have been taken away, if he wishes 
to make a barren soil produce fruit, or increase the fertility 
of a fruitful field, or keep a very fertile field constantly at 
the same high degree of productiveness ; it tells him that 
the art of the agriculturist cannot simply consist in lower- 
ing the high productiveness of a field to the level of ordi- 
nary fertility, and in turning a fruitful into a sterile field. 

It is held as a fundamental principle in science, that 
every opinion, before it is admitted as true and taught to 
others, should first be established by proper proofs, which 
must not in any way run counter to undoubted truths, 
such as, for instance, that twice two are four, and not five. 



THEORETICAL AND PRACTICAL AGRICULTURE. 213 

Inferences and conclusions which are opposed to such 
truths are rejected by science, and it cannot surely be con- 
sidered an unreasonable request, to ask agriculturists to 
adopt the same principle as a guide in drawing their con- 
clusions. 1^0 w, it is actually upon these points that the 
conflict turns ; for the opposition is in reality directed, not 
so much against the facts and teachings of chemistry, as 
against the deductions drawn from them by common sense. 

The exposition of the scientific principles of agriculture 
is not a thing of yesterday, but dates so long ago as seven- 
teen years ; and the system of husbandry as taught in our 
agricultural institutions (see Letter I.), could certainly not 
have so long withstood the power of truth and common 
sense, had it not been separated from them as if by a wall, 
and defended from their attacks. 

The chemical truths in these Letters may be expressed 
by a simple formula, which, though bearing a somewhat 
mathematical appearance, is yet plainly intelligible to every 
one: 

P = F — E. 

The P in this formula stands for Produce (Corn, Pota- 
toes, Turnips, &c.); the F. stands for Food (Phosphoric 
acid, Potash, Lime, Ammonia, &c.) ; the E stands for Ee- 
sistance. 

Expressed in words the formula stands thus : 
The amount of produce yielded by a field corresponds 
with, or is proportionate to the quantity of food in the soil 
(to the conditions for the production of the crop), minus 
the sum of the resisting forces which hinder the production 
of the crop from the elements of food present. Let the 
letter F stand for six slices of an apple, and the letter E 
represent three fingers keeping a firm hold on two out of 
the six slices, there will remain only four slices free, which 
may be eaten by another person. 



214 THEORETICAL AND PRACTICAL AGRICULTURE. 

The entire contents of these Letters are simply a develop- 
ment of this formula. Everything that is said in them 
about amount and increase of produce, fertility, cultivation 
of the soil, manure, &c., is comprised in it. It is evident 
that if the formula be true, its application will embrace 
millions of receipts for the improvement of millions of 
fields, and for the continued production of the largest 
crops; and that the future prospects of our fields, and 
wealth and income of all agriculturists, will be dependent 
upon its strict and rational application. No one can then 
deny, that the development of this formula is of some im- 
portance to agriculturists, and its discussion of some value 
to them. 

Whatever progress has been made by practical agricul- 
ture for some thousands of years past in the knowledge of 
manures, is clearly referable to those true principles which 
constitute the basis and conditions for correct conclusions. 

Guided by a careful study of the elements of the food 
of plants, science, in the year 18-iO, pointed out to the 
\ agriculturist guano as one of the most infallible means of 
raising the produce of corn and flesh, and most urgently 
recommended its application. Before 1840, guano had 
never been used as manure on a European field. When 
the first vessel loaded with guano arrived at Liverpool, 
numerous experiments were made with the new manure, 
which proved failures ; and agriculturists were not agreed 
about its utility until they had practically tested its use. 
Since that time many hundreds of ships have passed to and 
fro, and have brought to the European Continent guano to 
the value of above 300,000,000 florins (£26,000,000) ; and 
within the same period there has been produced a surplus 
of more than 400,000,000 cwt. of corn, or of its equivalent 
in flesh. It is true, guano would have found its way to 
Europe even without the recommendation of science ; for 



THEOKETICAL AND PEACTICAL AGRICULTURE. 215 

a kind Providence makes the apple ripen in proper season, 
and if it drops from the tree and rots, the fault lies with 
man, or with the soil, if the seeds do not germinate. But 
guano would probably not have made its way so speedily. 
In the late seasons of sterility through which we have 
passed, it has been the means of alleviating the wants of 
many millions of men. 

The man of theory who predicted the effects of guano 
had not seen the favourable results of its application, which 
our "Nitrogen champions" had subsequently occasion to 
observe in England ; but the predictions of its utihty had 
been simply based on the results of its chemical analysis, 
and was only a corollary deduced from the principle, that 
it is indispensable to resk>re to the jield exhausted by the growth 
of corn the mineral elements taken away in the crops. 

Not pseudo-chemistry, but science, placed in the hands 
of the agriculturist the means of making phosphate of lime 
more readily available for the nutrition of plants, by treat- 
ment with sulphuric acid ; and the results of the practice in 
England for the last ten years have shown, that by the use 
of this means the amount of provender for cattle has been 
increased to the same extent as if the area of every field for 
green crops had been doubled. There have been produced 
since then, on the same area, many million cwt. more flesh 
than formerly, or its equivalent in corn. 

And the man of theory who advised the use of this 
means had not seen its effects, as our agricultural chemists 
in England have seen them ; but he had simply inferred 
them from the principle, that the action of a manuring agent 
in a given time m^ust increase in proportion as its surface in- 
creases. 

Whatever practical agriculturists^ and agricultural socie- 
ties may do, whatever they may resolve at their annual 
meetings, every penny spent will be thrown away, and 



216 THEORETICAL AND PRACTICAL AGRICULTURE. 

every year of experimenting will be in vain, so long as 
these practical men will not submit to the teachings of true 
experience, to the rules of logic or of common sense : from 
the instant they shall so submit, science will be theirs. 

There exists a receipt for insuring the fertility of our 
fields and the permanence of their crops, and which, if pro- 
perly and consistently applied, will prove more remunera- 
tive than all the expedients that have ever before been 
resorted to by agriculturists. It consists in the following 
rule: 

Every farmer who takes a sack of corn, or a cwt. of rape, 
turnips, potatoes, &c., to the town, ought, like the Chinese 
coolie, to carry back with him from the town an equal (or, 
if possible, a larger) quantity of the mineral constituents of 
the produce sold, and restore them to the field from which 
they have been taken. He should not despise the peel of a 
potato, nor a straw, but always bear in mind that that peel 
may be wanting to form one of his potatoes, that straw to 
form one of his ears of corn. The cost of carrying these 
matters to his fields is trifling, and the investment is as 
safe as a savings-bank, and highly productive withal. The 
fertile area of his field will, in the course of ten years, be as 
it were doubled ; he will produce more corn, more flesh, 
and more cheese, without having, on that account, to 
bestow greater labour and time upon the cultivation of his 
land ; he will be less anxious about his fields, and need no 
longer keep his mind constantly on the stretch for some 
new, unknown, and imaginary expedient to preserve their 
fertility in some other way. 

All the proprietors of the soil in every great country 
ought to form a society for the establishment of reservoirs 
where the excreta of men and animals might be collected, 
and converted into a portable form. Bones, soot, ashes, 
lixiviated and unlixiviated, the blood of animals, and offal 



THEORETICAL AND PRACTICAL AGRICULTURE. 217 

and refuse of all kinds, ought to be collected together in 
these establishments, and prepared for transport by the 
society's own officials. 

To render the execution of a plan of this kind possible, 
government and the police authorities should take measures 
to insure the proper construction of latrines and sewers in 
towns, to guard against the waste of the night-soil, &c.* 
This must of course be a preliminary arrangement ; but, 
when once made, an annual subscription of half-a-florin 
from every farmer, every peasant in the land, will suffice to 
call into existence establishments of this kind in every 
town ; and there can be no doubt that these establishments 
will speedily become self-supporting, if every agriculturist 
will only make up his mind to act strictly upon the advice 
here given. 

Agriculturists must not rely upon guano ; its price at the 
present time, as compared with an earlier period, is already 
doubled ; and no sensible man would entertain the idea of 
making the production of an entire country dependent on 
the supply of a foreign manurcf 



* Judicious arrangements have already been adopted last year in Munich, 
by the Minister of the Interior, with a view to the improvement of the sani- 
tary condition of the city. The success of these measures will materially 
depend upon the manner in which the proprietors of the houses appreciate 
and aid the wise intentions of government, 

f It is almost to be feared that guano will play a momentous part in his- 
tory. "When it is considered that one cwt. of that manuring agent contains 
the effective mineral constituents of between 25 cwt. and 30 cwt. of wheat, 
or of an equivalent amount of some other produce, and that, when used as 
manure, it produces, in a succession of crops, a corresponding quantity of 
elements of food, some conception may be formed of the immense value 
which the guano beds of America possess, with reference to the production 
of corn in Europe. From the enormous increase of the population of Lon- 
don, and other large cities of Great Britain, the loss which the English fields 
sustain annually in the main conditions of their fertility, is every year becom- 
ing more and more considerable ; and it would appear that the obstacles 

10 



218 THEORETICAL AND PRACTICAL AGRICULTURE. 

Agriculturists must in the first place learn to turn to the 
best account all the means and resources at their command ; 
when they have done this, but not till then, will chemistry 
be able to do them good and useful service. But so long 
as they expect this science to present them with potent 
charms for fertility, there is no help for them. They must 
bear in mind, that wherever success does not attend a good 
cause, the fault lies in want of energy in using the proper 
means ; for these are always to be found.* 

which ogpose the collection of the human and animal excrements are alto- 
getlier insurmountable, at least as regards London. It is evident, therefore, 
that England, in order to remain permanently a corn-growing country, 
requires a free and plentiful supply of guano (even now Great Britain con- 
sumes nearly nine-tenths of all the guano brought to Europe). Fifteen 
years ago the American agriculturists looked down upon guano with a 
species of contempt ; but things have greatly altered since then ; and it is 
said that last year about eight million cwt. of that manuring agent were 
imported into the United States. In the actual position of English Agricul- 
ture, America, by her guano-beds, rules the prices of all the corn-markets of 
Europe, and more especially in England; and should circumstances ever 
arise to prevent the importation of guano into England, a state of things 
would ensue in that country of which the consequences might be 
incalculable. Bloody wars have sometimes sprung from causes of much less 
importance. 

* If we ask the opinions of different persons on the question of " sewage," 
we receive contradictory answers. All manufacturers of super-phosphate of 
lime are quite agreed on the point, that only the fluid portions of sewage, or 
the matters dissolved in sewage water, are valuable in agriculture. They do 
not, in giving this opinion, deny the good effect of the solid matters^ but only 
mean to say that they are not worth the trouble of being collected for 
manure, because they are ready to deliver fi'om their manufactories these 
matters to agriculturists. The manufacturers of ammonia salts, and the 
dealers in guano, take an entirely opposite view. These hold that only the 
solid sewage matters are to be looked upon as important. There can, how- 
ever, be no doubt that both the fluid and solid matters are valuable for 
agriculture. 

" The use of these fertilising matters is not confined to the estates and farms 
in the immediate vicinity of the centres of population and consumption. Our 
peasants go long journeys with their wretched carts to seek substitutes for 



THEORETICAL AND PRACTICAL AGRICULTURE. 219 

the deficient quantity of their farm-yard manure. The industrious peasant 
of Lucca is worthy of ranking with the Chinese coolie. Enjoying the bless- 
ings of irrigation within a circle of twenty-eight miles (English), the former, 
who has never even heard of the name of guano, manges to reap two crops 
in the year ; and yet never allows his land to lie fallow. He goes, however, 
with his cart, not only to the neighbouring town of Lucca, but even as far as 
Pisa and Leghorn, to collect the contents of the sewers, with the aid of which 
he produces, by indefatigable labour, marvellous crops, and raises food suffi- 
cient for the most dense population of the old duchy. The boats of Viarreggio 
carry from this port the goats' dung of the Maremma, to manure the olive trees 
of the Apuan coast." 

" From the peculiar circumstances m which our Maremmas are placed, they 
are debarred from the benefit of a like restitution of the conditions of fertility. 
Cultivation slowly improves, and the amount of produce reaped increases 
every year; but the scanty and migratory population of a soil, deserted on 
account of the miasmatic exhalations, cannot yield an amount of fertilising 
matter in proportion to the quantity carried off from the land. The gradual 
introduction of the system of the rotation of crops might slowly lead to the 
same impoverishment of the soil which has resulted in other places from the 
'high system of farming.' The apprehension lest this should in reality be the 
result of it, has by no means escaped the attention of the proprietors and 
cultivators of the soU in the Grand Duchy, who are so earnestly endeavouring 
to make agriculture flourish in these parts. The barrenness and desolation 
which has so long been the fate of the Maremma may, perhaps, be partly 
attributable to the spoliation system of farming pursued by the ancient Romans 
and Etruscans." 

" Agriculture in Tuscany, then, is based upon the principle of restoring to 
the soil those elements which science points out to be the most efficacious for 
the growth of plants ; and in this respect it is far ahead of the system pursued 
in other countries," Sec. — {Set nuove ktiere chimiche sulV agricultura di Ckusto 
Liebig, compendiaie et annotate de Gustavo Dalgas, Dr. Fhilosoph. Firenze^ Felice 
Paggi, 1858, p. 93.) 



APPENDIX. 



TO LETTER VI. 

In the cultivation of grass for a season merely, or in the planting of 
a particular kind of grass or of several sorts combined, the nature of 
such grass or grasses is essentially a matter for consideration, but not 
so in the case of the sward. Just as the beech tree when standing 
alone covers a broad space, and nearly sweeps the earth with its richly- 
leaved boughs, while a number of the same trees, standing closely 
together, tower upwards like columns, and merely clothe themselves 
with branches and leaves at the very summit, so in the sward of the 
natural meadow, plant closely clings to plant, altering its very struc- 
ture in yielding to the law of necessity. 

Those kinds of grasses which do this in a less degree, such as 
meadow soft-grass {Hblcus lanaius, L.), are on this account less suited 
for meadow plants, whilst others, though coarse-tufted, such as cocks' 
foot-grass (Dadylis glomeraia, L.), and even tm-fy hair-grass {Aira 
caespiiosa, L.\ form large separate tufts only with an inferior sward. 

In the spring of 1857, I examined a patch of quite new grown turf, 
which was exceedingly fine and close, taken from the ground facing a 
ditch used for the draining of a large meadow ; I found on an area of 
11-85 square in. Hess., 265 grasses. On an older piece of turf taken 
from the irrigated meadow having an area of 14*4 square in., I found 
210 grasses and 12 other plants ; and on another patch of an area of 
13*2 square in., 150 grasses and 25 other plants. 



222 APPENDIX. 

These high figures sufficed to confirm me in my original supposition, 
that only a small portion of the store of plants is completely developed 
in one year, and that a change of plants takes place according to the 
altered influences of the atmosphere and the soil ; a fact which, ac- 
cording to Thaer, has been already noticed by others, and, as it ap- 
pears, was also observed by Schwerz. 

It is well known that many plants, when a condition indispensable 
to their perfect development ceases to exist, as for instance, where the 
over-hanging shade of growing timber, or a too great clearance, pre- 
vents their growth, will for years retain existence by the extension of 
their roots, remaining as it were at a lower stage of growth, till there 
is a return of more favourable circumstances for their development. 

Thus we find that cleared ground will frequently become imme- 
diately covered with plants, many of which, being perennials, such 
as the raspberry, could not have sprung from seed. I have proved 
that this state of things is very general and is not confined to cases 
alone where the impediments to the growth of the plants are so con- 
siderable, but that it applies also more especially to grasses, and is of 
the highest importance in the cultivation of meadows. 

Every one knows that ash draws forth clover plants (which, like the 
grasses, do not flower the first year) ; and likewise that after manuring, 
other kinds of grasses make their appearance on the meadow. I ob- 
served on a plot manured with so-called acid-phosphate of hme, the 
almost exclusive growth of a single kind of grass, French rye-grass 
(Arrhenaterum avenaceum), which came up in thickly serried blades, 
whilst on the unmanured ground but a few stalks presented them- 
selves. 

I have examined the stock of plants on meadows at the time of the 
development of the culms. I had pieces of turf carefully cut out, 
measured, and the soil washed away, which left a dense mat of closely 
interwoven roots. There were found on one square foot, Hess. in. : 

1. Irrigated meadow near Zerby: dry patch. Predominant: — Bromus 
mollis, L,, ei Arrhenaterum avenaceum P.B. Size of sod, 22 square inches ; 
containing 472 plants; in stalk, 36. 



APPENDIX. 223 

2. Irrigated meadow, same place: wet patch. Predominant: — Glyceria 
fluitans. Size of sod, 20 square inches ; containing 1230 plants; in stalk, 20. 

3. Dry unirrigated meadow, near Fehlheim : manured with compost. Pre- 
dominant: — Agrostis alba et vulgaris. Size of sod, 56 square inches; con- 
taining 668 plants, of which there were 601 grasses and 67 other plants; in 
stalk, 66. 

The other plants consisted of Lysimachia nummularia, BeUis jperen- 
7iiSj L., Veronica chamcedris, Ranunculus , Rumex. 

4. Irrigated meadow, near Fehlheim, somewhat mossy. Predominant: — 
Poa irivialis, Festuca jpratensis^ Avena jiavescens, Fesiuca rubra, Agroslis vul- 
garis. Size of sod, 55'25 square inches; containing 730 plants, of which 
there were 584 grasses, 182 other plants; in stalk, 125. 

The other plants consisted of Plantago, Daucus, Veronica, Rumex, 
Ranunculus, Chrysanthemum, Trifolium repens, Lathyrus. 

5. Meadow near Balsbach, in the Hessian Odenwald (counted by Peter 
Kreuz, of that place). Predominant : — Agrostis siohnifera and Anthoxanthum 
odoratum. Size of sod, 1 square foot; containing 1176 plants, of which there 
were 1070 grasses, 56 clover, and 80 other plants; in stalk, 38. 

6. Meadow near Balsbach, in the Hessian Odenwald (counted by Peter 
Kreuz, of that place). Predominant: — Lolium perenne, Festuca pratensis, 
Dactylis glomeraia. Size of sod, 1 square foot; containing 790 plants, of 
which there were 710 grasses, 80 other plants (before the second cutting, 
without stalks). 

7. Meadow near Balsbach, in the Hessian Odenwald (counted by Peter 
Kreuz, of that place). Predominant: — Festuca rubra, Agrostis stolonifera, 
Anthoxanthum odoratum, Cynosurus cristatus. Size of sod, 1 square foot; 
containing 920 plants, of which there were 800 grasses, 120 other plants ; in 
stalk, 14. 

In numbers 5, 6, and 7, an entire square foot of sod was examined, 
which must have been a most arduous and laborious undertaking. 
The examiner (Mr. Peter Kreuz) says : " We have carefully separated 
the single plants, and to guard against mistakes, collected them in little 
heaps of 10, and afterwards in heaps of 100 plants, by putting 10 of 
the small heaps together." 



224 APPENDIX. 

8. Unirrigated meadow in the parsonage garden of Hohenstein : not irri- 
gated, mossy, with tolerably dry soil (counted by the Rev. Mr Snell, of that 
place). Predominant : — Alopecums, Badylis, Arrhenaterum avenaceum. Size 
of sod, 1 square foot, Nassau measure; containing 1040 plants, of which 
there were 832 grasses, 80 clover, 128 other plants; in stalk, 208. 

The other plants consisted of Planiago, Leontodon, Veronica, Lysi- 
machia nummularia. 

9. Dry unmanured meadow, near Fehlheim : weedy (counted by the author). 
Size of sod, 60 square inches; containing 379 plants to the square foot 
(Hessian), of which there were 276 grasses, 103 other plants; in stalk, 0. 

The other plants were Planiago, Prunella vulgaris, BeJlis, Ranuncu- 
lus, HieraciuTn, Veronica, Carex. 

Sinclair found on one English square foot, equal to about 1^ square 
foot, Hessian in : 

Yery rich natural meadow, 

at Endsleigh, . 
Rich old meadow, at Croft' 

church. 
Old meadow at Woburn, 
Old meadow at "Woburn, soil 

moist, surface mossy, 
Irrigated meadow. 

If we place the figures given by me by the side of those of Sinclair, 
properly reduced, we find that they agree as closely as can well be ex- 
pected : 

Hanstetn. Sinclair. 

1230 1200 

1176 — 

920 — 

790 726 

730 — ■ 

668 666 

472 606 

379 423 



:\ 



Plants. 


Grasses. 


other plante. 


1000 


940 


60 


1090 


1032 


58 


910 


880 


30 


634 


510 


124 


1798 


1702 


96 



APPENDIX. 225 

This comportment of the grasses is of the highest importance; 
it explains the fact of the permanent duration of natural meadows, 
and the certainty of their yield; it is this property that causes " the 
sward, which in the temperate zone neither heat nor cold can destroy, 
to be clothed with perpetual verdure." 

The large number of plants which are in a low stage of develop- 
ment, await, as if in a slumbering state, the coming of the time for 
their perfect development ; the more important plant is in such case 
replaced by the plant of lesser pretension, until the conditions of per- 
fect growth have again returned for the former. — H. Hdnstein — Jour- 
nal for Agriculture, IX. year, p. 270. 



ADDENDA. 



SHOULD THE FARMER BE EDUCATED? 

Although it has been said that every farmer should not 
try to be a geologist, meteorologist, chemist, etc., or study 
medicine to be his own doctor, or law to make it unneces- 
sary to employ a lawyer, or theology with the sole view of 
doing his own preaching, still there is little doubt that all 
general information, and the more exact the better, has a 
great tendency, if well applied, to be useful to the farmer's 
best interests. Every cultivator desires to gather from the 
soil, at small expense, large crops, with as little injury as 
possible to the source of production. He cannot do this 
without being familiar with general principles in the 
various departments of his profession, and understanding 
most thoroughly the art of agriculture. The man who 
grows crops well must understand the nature of soils, 
which certainly includes more research than would enable 
him to arrive at the sage conclusion that one is sandy and 
another clayey, etc. Then what should be the extent of 
the farmer's education ? Who will answer the question ? 
One person is found fault with for being " too scientific ;" 
another, for not being enough so. Now, suppose all 



228 ADDENDA. 

should practise with science, cast away prejudice, and seek 
to apply knowledge for its own dear sake, we might hope 
for rapid progress in mental acquisition, national wealth, 
and prosperity. If the farmer was not placed in such 
close relation with almost every department of science — in 
a word, with Nature's endlessly beautiful and diversified 
works — it would not be difficult to define what should be 
the extent of his education. Let us apply truths as fast as 
we discover them, and not find fault with the man of 
science because he cannot supplant the Divine Architect. 
It would be impossible for any agriculturist, during his 
whole life, to study any one department bearing on his 
calling to its fullest extent ; and, therefore, who will ven- 
ture to advise when he shall cease to explore and grieve 
over the exhaustion of the realms of knowledge ? 



' SCIENCE AND COMMON SENSE.— P. 215. 

Liebig truly says, " Whatever practical agriculturists and 
agricultural societies may do, whatever they may resolve 
at their annual meetings, every penny spent will be thrown 
away, and every year of experimenting will be in vain, so 
long as these practical men will not submit to the teachings 
of true experience, to the rules of logic or of common 
sense ; from the instant they shall so submit, science will be 
theirs." 

How very different is the meaning of the expression 
** common sense " when unfolded in the light of science as 



ADDENDA. 229 

compared with its ordinary acceptation. The words, as in 
everj-day use, are of little value, but how telling is their 
effect when under the control of science, as used by Baron 
Von Liebig. Some agricultural writers speak of " common 
sense unaided by science ;" which seems to be a desire to cater 
to the prejudices of an uneducated class of farmers. This 
is beneath the dignity of a man, who should be guided by 
truth alone. The expression common sense, as some people 
use it, is exceedingly indefinite; for every person, from 
the fool to the philosopher, has a common sense standard 
of his own, differing from that of every other man ; and 
as no two minds are exactly alike, the varieties of common 
sense are in proportion to the number of persons who ad- 
mit such faulty expressions. Science has to do with the 
observation and classification of the truths or laws of 
nature. Common sense, as in every-day use long ago, 
said the world was flat ; science has proved it to be round. 
She has resolved the once mysterious soil into the constitu- 
ents or elements of plants, and told us of their qualities 
and quantities. Common sense, as used by the crowd, 
never said a word on the subject. Why should any one 
say, as we find in some of the books, that " the roots of 
plants themselves go out in quest of that food," which com- 
mon sense, unaided by science, tells us is " by them communi- 
cated to the plant?" To follow this style of argument 
would be very uncommon sense. Agricultural writers 
should not draw lines of distinction between the practical 
intelligent farmer and scientific man. Science and practice 
should come together ; for in exact proportion to the union 
between them will agriculture prosper. Why repudiate 



280 ADDENDA. 

science, and in the same breath say, " If you wish to make 
a youth a shoemaker, you must first send him to school in 
order that his mind may be expanded and prepared to re- 
ceive the seeds of practical instruction." If the farmer is 
to depend so much on " common sense," and so little on 
science, why does not the shoemaker, feeling that there is 
nothing like leather, graduate with the wax-end in his 
hand ? which would be carrying out the maxim, " Ne sutor 
ultra crepidamy Even tinkers claim that their collabora- 
teurs should be men of common sense, but it is their busi- 
ness to bottom kettles. A tinker need not trouble his mind 
with the science of mining or the manufacture of the useful 
metal which he hammers. The farmer who is averse to 
scientific education, is but an agricultural tinker. Let the 
cultivator of the soil arouse to the dignity of his calling. 

Let it not be forgotten that science has made the rough 
places smooth, and interlaced the face of Christendom with 
railroads, over which the commerce of nations is sent to 
and fro for the use of busy man. She has prepared the 
way for, and sent the steam-engine through, the trackless 
forest, disturbing the haunts of the red man and wild beast 
with the sound of civilization, and, like Prometheus, 
brought the fire from heaven to be the errand-boy of the 
human race. 



ADDENDA. 231 



AaRICULTURAL MACHIKES. 



If necessity be the motlier of invention, it will not be 
denied that she possesses to some extent parental protection 
over discovery. Invention and Discovery are members of 
one family. In an agricultural point of view, necessity, in 
this country, and indeed many others, has not caused the 
gathering of knowledge for general application to the cul- 
ture of the soil. New land is so easily got and so produc- 
tive, except in a few places, that the necessity for modes of 
culture other than those of the most common kind has not 
been generally felt by landed proprietors. Let us think 
of the growing want for soil on which to operate, by the 
rapidly increasing home population, immigrants, and the 
general introduction of labor-saving machinery. Necessity 
has been, in this case, of great value to the nation in 
developing its resources. The demand for labor-saving 
machinery has called into action the intellect of the land, 
which has invented and constructed for agricultural pur- 
poses, reaping, mowing, and threshing machines, etc., all 
suited for well cultivated soil, free from stumps, and equally 
so to all other parts of the country, as fast as they become 
so. The mowing machine lays a basis for more animal 
food, for by it the material necessary for its production may 
be gathered more easily. The fact that the agricultural 
machinery of to-day — should there be no more inventions 
— applies to soil all over the globe, may assist us in form- 
ing a correct estimate of the future vastness of agricultural 
operations. 



232 ADDENDA. 

At a great national exhibition, as for instance, like that 
of the Fair of our American Institute, it is exceedingly in- 
teresting to examine the labor-saving contrivances that 
come from the mind, and to see visitors looking at the life- 
like things, whose muscles of iron and steel perform so 
important a part in the development of national wealth and 
prosperity. Here may be seen the labors of the brain- 
wearied inventor, of whom it has well been said : 

"In the great scale of being which with God began, 
there is no created intelligence which approaches him in 
dignity. Next to the eternal Architect, at whose bidding 
the vast machine of the universe came into being — whose 
cunning hand moulded the wondrous mechanism of our 
frames — he stands ; creating out of the airy fabric of the 
brain the magic forms which never die. Look back upon 
the track of time, and what survives its wreck ? Here- and 
there upon the strand a solitary monument of literature, 
of marvellous beauty — out of the millions of books which 
have delighted their millions of men — survives to tell us 
that the rest have perished ; but every creation of the 
inventor, from the first dawn of time to the present hour, 
exists among us. As time rolls on it but widens the circle 
and adds glory to the memory of those whose works sur- 
vive them. The names of millions have perished, but the 
thoughts they thought will never die. Their blessings, 
like the air and light, are now our daily life ; but when we 
reflect, we know there was a time when they did not exist, 
and that the art of the engineer produced them all. Civi- 
lized men have reared their monuments and worship at 
their shrine. The splendid temple whose lofty arches 



ADDENDA. 233 

sprang into tlie skies, above the trees of tlie forest, and the 
palaces of kings erected by a great nation and devoted to 
them, is the world's tribute to genius — the acknowledg- 
ment of the mastery of the mind. As I stood within its 
crystal walls, and gazed into its gorgeous dome, the 
shadows of the mighty dead in solemn pomp passed by. 
Archimedes, and Bacon, and Watt, and Fulton, Gutten- 
berg, Gralvani, Franklin, and Torricelli, and a host of other 
immortal ones; and in shadowy outlines their mighty 
works — the printing-press, the steam engine, the electric 
wire, the foaming steamer, the unerring compass, the 
roaring cannon. The powers of the earth attend their foot- 
steps — the lightnings of heaven obey their commands. 
My soul drank in the inspiration of the fairy scene, and I 
felt the dignity of his calling." 

Stop the machinery of the world for a day, and a blank 
would be left in its history that would throw a gloom over 
coming ages. Even the plough and less respected plough- 
boy should they forget their labors, fields of golden grain 
would be things of the past. The labor saved by machinery 
is applied to new purposes either mental or manual ; and 
the consequence is new development. The inventor of a 
machine to do the work of many men and oxen is a useful 
laborer. 



234 ADDENDA. 



" MORE BREAD AND MEAT.— P. 1. 

" The most urgent problem wliich the present day has 
to solve," says Liebig, "is the discovery of the means 
of producing more bread and meat on a given surface, to 
supply the wants of a continually increasing population. 
The most important social questions are bound up in this 
problem, which science is expected to solve." The problem 
spoken of by the great Liebig has a world-wide significance. 
Let us look at some of its facts in their relation to our 
own country with a view to showing the necessity for a 
rational system of agriculture. The production of more 
bread and meat is of daily increasing importance. We 
want more in time of war and peace to sell to other people. 
The increase of animal food is not keeping pace with the 
increase of population. We have no figures of more recent 
date than those given below, which, if not exact^ come near 
enough to the truth for general purposes. There is every 
reason to suppose that the next census would show more 
strongly the necessity for growing more meat. The follow- 
ing table gives the number and increase of cattle in the United 
States. 





1840. 


1850. 


Horses and mules, 


. 4,385,399 


4,896,050 


Neat cattle, 


. 14,971,586 


18,378,907 


Swine, 


. 26,201,293 


30,854,213 


Sheep, 


. 19,111,374 


21,723,290 



The increase of 'population has been S5 per cent.j while that 
of cattle has been only 20 per cent. 



ADDENDA. 235 

In New England, New York, New Jersey, Delaware, 
Maryland, and Virginia, tlie three principal meat-producing 
animals, cattle, slieep, and swine, have been rapidly de- 
creasing, as is shown by the following tables : 

DOMESTIC ANIMALS IN THE OLD STATES. 





1840. 


1850. 


Decrease. 


Horses and Mules, 


1,612,883 


1,529,189 


83,694 


Neat Cattle, 


6,172,569 


6,033,841 


138,728 


Swine, 


6,897,396 


4,909,334 


1,988,062 


Sheep, 


11,872,622 


5,450,678 


6,421,950 



The population has been increasing in the Old States, 
while the meat-producing animals have been decreasing. 

It is now quite natural to look to some of the New States 
for a supply. The following table will apply to the States 
of Indiana, Ohio, Kentucky, Illinois, Tennessee, and Mis- 
souri : — 

DOMESTIC ANIMALS IN THE NEW STATES. 





1840. 


1850. 


Increase. 


Horses and Mules, 


1,804,092 


2,116,160 


312,068 


Neat Cattle, 


4,307,952 


5,280,433 


972,481 


Swine, 


11,726,209 


13,843,041 


2,116,832 


Sheep, 


5,197,906 


8,435,658 


3,237,752 



The increase of animals in these States for the ten years 
ending 1850, is shown in the above table. 

Our exports of breadstuffs and animal products were as 
follow : — 



236 ADDENDA. 

1836— '40 inclusive, $63,050,000 

1842— '46 " ..... 110,521,000 

1847— '51 " 194,330,000 

1852 — '56 " 233,697,000 

From the foregoing it will be seen that our exports 
during the periods named were gradually increasing, nor 
is there any reason to suppose that the markets abroad are 
falling off in their demand. These, of course, have their 
influence on the money value of bread and meat. Every 
pound of salted meat sent to other countries will affect the 
price of animals in the most distant parts of the United 
States. This puts money in the pockets of producers, while 
it increases the cost to less productive consumers who live 
in the towns and cities. By looking at the first table, which 
refers to the numl:jer and increase of cattle in the whole of 
the United States, it will be seen that the increase has been 
only about twenty per cent., whereas the increase in the 
population has been thirty-five per cent. These are strange 
facts to be true of the cattle raised on the soil of the United 
States. And we are beginning to feel their result, for we 
have had to pay more and more for meat — the price has 
been gradually increasing for a long time. 

Many farmers near large towns and cities cannot afford 
to make butter and cheese from their milk, on account of 
the demand for it, and the facility of getting it to market 
by railroads. This milk business is destructive to cattle ; 
the calves as well as the milk are sent to market; and 
these facts, of course, have their influence on supply and 
demand. 



ADDENDA. 237 

It is impossible that the prices of meat should long 
continue high in any town or city of importance ; for, if 
the supply is abundant, the prices soon become equalized 
all over the country, less the cost of transportation, the 
means of getting it to market are so easy. The increase 
in prices has hardly caused us to eat less meat ; and as the 
quality is improving with our appreciation, we do not break 
up habits already formed — those of a meat-eating people. 

These facts and figures do not show that the cost of 
meat is owing to an unusually short supply of animals for 
any one or two seasons, short crops, increase of foreign 
demand (although this has had its influence), fluctuations 
of trade, or to causes of much importance besides the 
disproportion between the number of animals and our 
rapidly-increasing population — that is to say, the results 
have been subject to the invariable law of demand and 
supply. The principle in this question is easily under- 
stood. If a family of six persons have a given quantity 
of meat which is equally divided, each person will have 
twice as much for his share as would the individuals of a 
family of twelve persons from the same quantity. The 
same facts are true of a nation, which is nothing more 
than a big family. Although animals are increasing in 
the great North- West, there is a want on the part of the 
increasing population of all ike States^ not being supplied 
at the prices of by-gone days ; nor is there any likelihood 
of an immediate remedy. That meat will cost less under 
this state of things, for a long time to come, is impossible. 
We take it for granted that this increase in price for many 
years past, as figures show to be true, puts this subject 



238 ADDENDA. 

entirely beyond speculation, excepting, perhaps, the sud- 
den rise and fall of ordinary transactions of commercial 
life, the details of which cannot be reasoned upon ; but 
they are hardly necessary to throw light on the future 
operations of the meat-grower and cattle-breeder, in mak- 
ing their calculations, with a view of finding a remunera- 
tive market. . It is for these reasons, in part at least, that 
we ought to regard what Liebig has to say on soil culture, 
and be on the look-out for the best machines in the shape 
of animals, as well as for all facts connected with breed- 
ing, feeding, and caring generally, with the view to pro- 
duce the largest possible amount of meat, of the best qua- 
lity, at the smallest expense. It becomes a self-evident 
fact that we must pay more for meat, use less of it, or 
increase the supplies. This is at least encouraging to in- 
telligent farmers. More attention must be paid to produc- 
tion. This may be done in part, not only by increasing 
the proportion of the industrious over the idle consumers, 
but by exciting the best efforts of those engaged in agri- 
culture in favor of the most rational system of practice. 

It is pleasing to see every little while, statements in Eng- 
lish journals relative to the purchase of choice animals for 
the United States. The gentlemen who make the selec- 
tions are invariably spoken of by the British press as spar- 
ing neither expense nor trouble to obtain the choicest ani- 
mals of the respective breeds considered worthy of special 
attention. 

But let the day soon come when the rich prairies will 
grow cultivated grasses to support the best kinds of stock, 
and to be no more consumed by fire. 



ADDENDA. 239 

The finer grasses should take the place of inferior ones, 
and green crops should be more grown. The culture and 
fertilization necessary for them are sure to prepare the way 
for other crops. 

The improvement in the quality of animal food in Great 
Britain and Ireland, since the general cultivation of turnips 
and other roots, is too well known to be spoken of more 
fully. The same facts will be true with us wherever the 
root crops receive proper attention. Before their introduc- 
tion into England the fattening of animals to perfection in 
that country was unknown. A slight increase in our ani- 
mals and crops would amount to more than the total 
expenses of the general government. In these days of steam 
cars, steam ships, electric telegraphs, arctic expeditions, and 
voyages round the world, too little attention is paid to the 
grand source of human subsistence for a thousand million 
of men, and it is a matter of some importance to every human 
being to know that he will get his daily bread. It is the 
first petition in the prayer which our Master left us as an 
example. " Give us this day our daily bread " means much 
in the domestic economy of a nation — how much more so 
among nations when ships freighted with bread are passing 
every ocean across the track of ships of war, one on its mis- 
sion of peace and plenty — the other on its mission of war- 
fare and death. At such a moment this question of more 
bread and more meat from the same number of acres, with- 
out exhaustion, and with better directed labor, is a question 
of life, of power, and prosperity to our continent. 

"The increase of population on the Eastern Continent 
(says Mr. Jay in his Statistical Yiew of American Agricul- 



240 ADDENDA. 

ture), beyond the capacity of production, is investing the 
question of food in this age with a significance that never 
belonged to it before, and the growing demands for bread 
that come to us from Western Europe, give a world-wide 
interest to the statistics of American agriculture, far beyond 
that which they could derive simply from the wants of our 
own countrymen. 

*' Consumption has there overtaken production, and 
henceforth in England, France, Belgium, Holland, and a 
great part of Germany, the yboc? question will be the question 
that must take precedence of all others, as the regulator of 
commerce, and entitled to the first attention and the wisest 
treatment on the part of Grovernment." 

John Stuart Mill, the well known political economist, 
says : " Suppose, then, that the population of Great Britain 
goes on increasing at its present rate, and demands every 
year a supply of imported food considerably beyond that 
of the year preceding. This annual increase in the food 
demanded from the exporting countries, can only be ob- 
tained either by great improvements in their agriculture, 
or by the application of a great capital to the growth of 
food. The former is likely to be a very slow process from 
the rudeness and ignorance of the agricultural classes in 
the food-exporting countries of Europe, while the British 
colonies and the United States are already in possession of 
most of the improvements yet made, so far as suitable to 
their circumstances. There remains as a resource the ex- 
tension of cultivation, and on this it is to be remarked that 
the capital by which any such extension can take place is 
mostly still to be created. In America it is rapid, but not 



ADDENDA. 241 

more rapid than the population. The principal fund at 
present available for supplying the country with a yearly im- 
portaiion of food is that portion of the annual savings of 
Araerica which has hitherto been applied to increasing the 
manufacturing establishments of the United States^ and which 
may now possibly be diverted from that purpose to growing 
food for our market. This limited source of supply, unless 
great improvements take place in agriculture, cannot be 
expected to keep pace with the growing demands of so 
rapidly increasing a population as that of Great Britain — 
and if our population and capital continue to increase with 
tJieir present rapidity^ the only mode in which food can con- 
tinue to be supplied cheaply to the one is by sending the other 
abroad to produce ity 

" One fact," says the Mark Lane Express, " is clear, that 
it is to Western America that we must in future look for 
the largest amount of cereal produce." 

All these facts show the necessity for the production of 
more bread and meat. We shall be compelled to look into 
this subject with great care, and consider well the prepara- 
tion, fertilization, and cultivation of the soil, also the best 
varieties of seed, their preparation, time of sowing, changing 
of seed, quantity to be sown per acre, the habits of insects 
and modes of preventing them from injuring crops, etc. ; but 
above all when elements of fertility are taken from the soil 
to be sure to put them back again. 

Our field crops, such as wheat, rye, barley, oats, Indian 
corn, potatoes, the hay crop, etc., and stock are a necessity, 
and there is no thanks for us to grow them as well as we know 
how, for without them we should starve. But the vegetable 

11 



242 ADDENDA. 

garden is more of a luxury, though it will soon be a neces- 
sity. A farmer once knowing the value of good vegetables 
could not think of living without them. Why should not 
farmers generally, as well as citizens, eat cauliflowers, 
cabbages, pease, beans, lettuce, spinach, etc. ? But through- 
out the interior of this vast country, how few gi ve attention 
to these commonplace but useful products of our gardens. 

Many citizens pay extravagant prices for fruits, grown 
here, and imported from foreign countries. Some of the 
choice pears grown by a few persons in this country are 
sold now and then at the enormous price of a couple of 
shillings apiece. What harm would it be for farmers to 
grow the finest pears, apples, peaches, plums, apricots, 
nectarines, strawberries, and to eat them too, and when 
they have too much for themselves give the rest to their 
animals ? And while we supply our bodily wants with the 
necessaries of life let us not forget the charms of a flower- 
garden, and to render our homes as comfortable as intel- 
ligence and industry can make them. 



4 EXHAUSTION OF THE SOIL.*— P. 144. 

Our pilgrim fathers, a couple of centuries ago, began to 
till a somewhat stubborn but productive soil. They and 
their children took all they could get, but put little back 
again into the soil. This cannot be denied, while with all 
honor we must regard them as the pioneers of American 

* See pages 94, 108, 144, and 152. 



ADDENDA. 243 

agriculture. In the early history of this country our 
fathers found an immense expanse, and their urgent neces- 
sities calling for immediate action, they selected the most 
prolific spots and began to grow crops. Here were the 
washings of the highlands gathered, and localities like the 
Miami Yalley, the receptacles of vegetable decaying 
matter for centuries, were interspersed through the whole 
Atlantic slope. As men began to till the soil, and as fast 
as they exhausted one locality of such elements of God's 
bounty as were in a condition, from their solubility, to act 
as food for plants, they moved to new places rather than to 
properly work or fertilize old ones. They were not the 
servitors of their grandchildren, but with a vast country 
before them they chose to skim it, and as they drove the 
Eed Men westward, they found new fields for planting, 
and they " skimmed" the land. Here the great mistake was 
made, that of overrunning the soil to reap a few good 
crops that ended in impoverishing it, and this bad 
example has followed to the present day. Thus the 
Atlantic slope became a depleted expanse, and unprofitable 
with the modes of culture in practice. 

" A writer in the ' Year Book of Agriculture for 1855,' 
on the 'Alarming Deterioration of the Soil,' referred to 
various statistics of great significance in connexion with 
this subject. Some of them regarded Massachusetts, where 
the hay crop declined twelve per cent, from 1840 to 1850, 
notwithstanding the addition of 90,000 acres to its mowing 
lands, and the grain crop absolutely depreciated 6,000 bush- 
els, although the tillage lands had been increased by the 
addition of 60,000 acres. 



244: ADDENDA. 

"In Indiana the river bottoms, which used to produce 
an average crop of 60 bushels of corn to the acre, now pro- 
duce but 40. In Wisconsin, which is younger still, it is 
estimated that only one-half the bushels of wheat are now 
raised to the acre that were raised twelve years ago ; and 
the writer declares as the conclusion of the whole matter 
that the soils of New England, after all the admonitions we 
have received, are annually growing poorer, and that even 
the virgin lands of the Great West are rapidly becoming 
exhausted of their fertility." * 

The reader will find very interesting notes on the exhaus- 
tion of American soil on pages 179, 180, 181, 220. and 221, 
of this work. 

We choose rather to give the researches of others, as 
being most likely to convince the reader than the gleanings 
of one mind. In examining the foregoing facts in relation 
to short crops in some of the old states it will be well to 
consider that the ravages of insects doubtless deterred many 
from devoting the same area to the cultivation of wheat, but 
this fact could hardly be true of potatoes and some other 
crops ; still it would be well to bear in mind the probable area 
devoted to the crops referred to. There is no doubt that 
in the main the bad principle of exhaustion is too true. 
Liebig, in his " Familiar Letters on Chemistry," says : " Is it 
possible, after so many decisive investigations into the ori- 
gin of the elements of animals and vegetables, the use of the 
alkalies, of lime, and the phosphates, any doubt can exist as 
to the principles upon which a rational agriculture depends? 

* Jay's Statistical View of American Agriculture. 



ADDENDA. 245 

Can the art of agriculture be based upon anything but the 
restitution of a disturbed equilibrium ? Can it be imagined 
that any country, however rich and fertile, with a flourish- 
ing commerce, which for centuries exports its produce in 
the shape of grain and cattle, will maintain its fertility, if 
the same commerce does not restore, in some form of 
manure, those elements which have been removed from the 
soil, and which cannot be replaced by the atmosphere? 
Must not the same fate await every such country which has 
actually befallen the once prolific soil of Virginia, now in 
many parts no longer able to grow its staple productions 
— wheat and tobacco ?" 

Again he says, in the present work (p. 152), *' Let it be 
remembered that in Virginia there are vast tracts of land 
which at one time gave full crops of tobacco, Indian corn, 
and wheat, now lying waste. In 1850 the tobacco crop 
was eighteen million pounds less than in 1840. In 1850 
the average yield of wheat per acre was only seven bushels ! 
The American farmer despoils his field luithout the hast 
attempt at method in the process. When it ceases to yield 
him sufficiently abundant crops, he simply quits it, and, 
with his seeds and plants, betakes himself to a fresh field ; 
for there is plenty of good land to be had in America ; and 
it would not be worth his while to work the same field to 
absolute exhaustion." 

Thus it will be seen our agriculture is a system of con- 
stant depletion — it should be one of enriching and multi- 
plying resources, involving all the elements of the soil for 
the production of its fruits. 

Some few enlightened agriculturists of the Atlantic 



246 ADDENDA. 

border have restored worn out lands, and made them 
produce so bountifully, that in proportion to the capital 
and labor bestowed they make more money, acre per acre, 
than most farmers do from the unexhausted virgin soils of 
the West. 

Our wants are rapidly increasing. Whole districts, 
which thirty years ago gave an average of thirty bushels 
of wheat per acre, do not give ten bushels now. Until we 
stop eating bread this subject will not lose its interest. 
Why should we not grow as large crops, and of as good a 
quality as can be grown ? Does any one think good wheat 
can be grown on had soil ? Can the land give that which 
it has not ? 

If soil be too poor to pay for labor, the more of it the 
wheat grower tills without renovation, the poorer that 
land and himself will grow. 

The common opinion, that the soil of the West cannot 
be exhausted, is a great mistake. See how the crops have 
fallen off, as shown by the tables already given. Grain is 
carried to the cities, and the substances that made it are far 
away from their original source. The wheat crop of 1858 
robbed the soil of more than thirty million pounds of pot- 
ash, and sixty million pounds of phosphoric acid. But a 
small proportion of these elements is sent back to the 
soil. In Nature's economy nothing is lost ; but when man 
displaces things he should put them back again in their 
own places. A wise nation looks well to its agriculture, 
the great source of wealth. England dug the fields of 
Waterloo for human bones to enrich her soil. She sent 
her ships to foreign nations to bring home fertilizers. In 



ADDENDA. 247 

our agriculture we are a wasteful and soil-exhausting 
people. We are tenants of it but for life ; others will come 
after us. 

These are a few of the reasons, based on the had jprinciple 
of EXHAUSTION, why our crops in many districts are falling 
off. 

In some places land is so much exhausted that crops to 
pay for the labor cannot be grown. Again, we find soils 
that are very rich, but not in balance ; others are all that 
can be desired, but they are the fewest, excepting those 
we take from the hunting grounds of the red man, which 
are as new to us as the Garden of Eden was to our First 
Parents. 



MANURES.^ 



The much agitated subject of farm fertilizers continues 
to be of intense interest to every agriculturist, whether 
he be the mere laborer or the intelligent working farmer, 
whose motto is, " Practice with science." 

The investigations that are being made in the laboratory 
of the chemist, the farm-yard, and in the field of nature, 
operate to increase new interest in behalf of the superlative 
importance not only of the ordinary facts that attract 
attention, but also of the abstract truths that guide uner- 
ringly to the goal of perfection. 

The proper manipulation and fertilization of the soil 
furnish a great basis for national wealth and prosperity. 

* See pages 82, 108, 113, and 183. 



248 ADDENDA. 

It is only by means of manure that the equilibrium of 
the soil is restored. 

Like the farmers of England and other nations, we, too, 
have our strenuous and prejudiced advocates of the nume- 
rous modes of practice detailed by agricultural lecturers, 
manufacturers of agricultural books, as well as the novel- 
ties presented by the motley groups who constitute those 
assemblages denominated Farmers' Clubs. There is every 
shade of intelligence, from him who simply knows that a 
cabbage grows, and that he eats it, to the man of sound 
mind and sound body, who interrogates the silent opera- 
tions of nature to reveal to him structures of animal and 
vegetable life which are infinitely more beautiful and 
grand than the most ponderous artistic and imposing edifice 
that has ever been raised on the surface of our globe by the 
hands of man. 

Many men of as many minds, and a much larger number 
of theories, herald forth detailed accounts of faulty experi- 
ments, both orally and in printed periodicals ; the latter 
too often furnishing space which might remain unoccupied 
unless the greasy leaves of cookerj^ books were explored 
to grace the columns of the agricultural press, thus giving 
opportunity to laudation or abuse, either of which is far 
easier than the discovery of new truths. Some of the 
experimenters give good sense and the laws of nature as 
wide a berth as possible ; and their ill-directed labors furnish 
results more remote from truth than those of the most 
careless operator who tills the soil in the sweat of his brow. 

What vast amounts of labor and capital have been 
wasted in testing the value of fertilizers ! Farmers often 



ADDENDA. 249 

repeat tlie same experiments a hundred times, without its 
being known to one another that they do so ; but few of 
the results of their labor and capital are recorded. Experi- 
ments in the field, to be of value, must be exact ; if not, 
the tendency is to confuse rather than instruct. The writer 
once saw a neighboring farmer, when planting potatoes, 
use as fertilizers, farm-yard manure, guano, bone-dust, 
phosphate of lime, wood-ashes, plaster of Paris, salt, caustic 
lime, oyster-shell lime, water-slaked lime, the salt and lime 
mixture, and muck treated with salt and lime. Each was 
used separately, and in different parts of a field, having the 
same quality of soil throughout, and all done with the 
view of ascertaining what kind of manure was best for the 
potato! No attention was paid to the chemical or me- 
chanical qualities of the soil, its requirements, or those of 
the crop about to be grown. Men who thus blindly grope 
in the dark are the first to advocate, dogmatically, some 
extreme notion in relation to long or short manures, their 
treatment and modes of application. We freely admit that 
among the more intelligent of our profession may be found 
the advocates of long and short manures, the deep drainers, 
and the shallow drainers, as well as those who are favorable 
to the many intermediate shades of difference, without any 
modes in particular, being supported by the unanimous 
voice of agriculturists. The explorer should not be guided 
by the dupes of any theory in particular, but rather seek 
from every source that which seems most rational, and in 
best obedience to the unerring laws of nature. 

Chemical science has searched into the nature of the soil, 
the plant, and the air, and has shown that the word soil 

11* 



250 ADDENDA. 

means several substances rather than one, and that this is 
also true of the word plant^ and the word air. The soil 
and the air are the sources whence the material necessary 
for the building of the plant is obtained. 

Let it be remembered that the plant is not a single or 
simple substance, but is made up of several. If a piece of 
wood is burned, ashes will be the result. During the burn- 
ing some parts of the wood pass into the air. The house- 
keeper is in the habit of leaching the ashes to get Ije for 
making soft-soap ; a large per centage of this lye is potash, 
which came from the ashes, which came from the plant, 
which came from the soil on which the plant grew. This 
substance, potash, is one of the several which compose the 
ashes, such as lime, soda, and so forth. If, then, researches 
have shown that the absence of particular substances in the 
soil prevents some plants from growing successfully, and 
that supplying them in a proper manner restores fertility, 
we get at a simple and truthful explanation of a principle 
which must govern the action of all fertilizers. The word 
manure^ like the word soil^ means more substances than 
one ; and different manures must vary in action as they 
vary in composition, even if all other things are equal. 
These principles have their home in nature ; nor do we 
lay any claim to their discovery. The honor of this is due 
to greater minds. We are but the errand-boy giving the 
message to our readers. 

What is a manure ? It is that substance, whether simple 
or compound, solid or fluid, which yields to a plant food 
essentially necessary to its structure and development. 
According to this definition, water is a fertilizer, and such 



ADDENDA. 251 

constituents of tlie air and soil as go to support plant 
life. 

The farmer should consider what food is essentially- 
necessary to the plant about to be grown. 

What food is essentially necessary to the plant about to 
be grown ? 

From what source of advancement should the food be 
supplied ? 

What should be its mechanical and chemical condition 
in the soil ? 

These are a few of the important questions that relate to 
vegetable growth. 

Practice has fully satisfied experimenters that if any of 
the elements of which plants are composed be absent from 
the soil, they will not grow to perfection, and that the 
most perfect result can only be obtained from soils in exact 
balance. Qualitative and quantitative analyses of plants 
and soils have cast much light on these important features 
of the subject. The old notion that plants can create food 
is now abandoned by every intelligent mind. 

An animal fed on hay and oats will not furnish in its 
excreta the precise constituents, in the same relative pro- 
portions to each other, as they exist in the food. 

All the most valuable, most needed, and ready-to-he easily 
assimilated portions, such as are in an advanced condition, 
go to increase the size or bulk of the animal, or to make 
up for the wastage of the system. All that part of the food 
known as starch and gluten, or a very large portion of it, 
is not to be found in the excreta, unless the animal be 
over fed. The elements of farm-yard manure are not in 



252 ADDENDA. 

as advanced a condition as many of the crops to whicli 
they are applied, but many of them are on the very next 
plane of existence in the scale of progression, and must, 
therefore, be particularly suited for the production of the 
same plants as those from which they arise, and for all 
others of an analogous newness of creation. 

This principle must be clearly understood, and admitted, 
before the reader will be prepared to comprehend the ra- 
tionale or method of treating manures. Every vine-grower 
knows that the inorganic substances of the soil that go to 
make the wood of this year will be rendered fit pabulum 
for the fruit of next year, if made soluble by natural pro- 
cesses. Thus, the vigneron cuts the trimmings of his 
grape-vines, with an ordinary straw-cutter, and after hav- 
ing buried them in damp soil during winter applies them 
in the spring around the roots of the growin gvines, and 
increases the amount of fruit by doing so. 

Now, it must be evident, that when these cuttings are 
applied to the root of the same vine from which they were 
removed, no new inorganic matter is added to the soil, 
but it is simply that the same inorganic substances are 
replaced in the soil after having been progressed, by once 
assuming the form of wood, and that, therefore, without 
any increase of quantity, but only from superior condition, 
that the increased amount of fruit occurs. If this principle 
be correct, a hay crop undergoing decay beneath a soil 
where hay is intended to be raised for its seed, the 
quantity would be greater than from a less advanced 
manure, and simply because the constituents of the hay 
were ready for re-assimilation ; and it is to this fact that 



ADDENDA. 253 

stable manure, in no small degree, owes much of its 
value. 

Liebig, on a strictly cbemical basis, truly says, that 
"The solid and liquid excrements of an animal 
aee of the highest value as manure for those 
plants which furnished food to the animal." 

For a full understanding of the value of farm-yard 
manure, it will be necessary to consider its source and 
composition, and causes for the changes it undergoes, as 
compared with the integrants of the materials from which 
it arises. 

Plants receive support from the soil ; they nourish 
animals ; but certain portions, not appropriated, are known 
as liquid and solid excrements. 

The analysis of any specimen of farm-yard manure 
cannot be viewed as a universal standard of comparison. 

The peculiarities of animals as mere machines, the 
quantity and kinds of food consumed by them, their age, 
amount of exercise, climate, season of the year, the bear- 
ing of young, the giving of milk, and a variety of other 
circumstances, have a great influence on the composition 
of manures. The drainage of some compost heaps is 
exposed to rains, evaporation, or permitted to flow away 
to creeks. 

Others are carefully protected, but parts of them may 
abound in straw. Occasionally, farmers permit their cattle to 
roam and feed in the farm-yard, and they often waste as much 
food as they consume. How difficult, then, is it to select a 
sample for chemical examination, the analysis of which will 
be an exact representation of farm-yard manures in general. 



254 ADDENDA. 

The loss of ammonia during the preparation of farm- 
yard manures has been and is attracting much attention. 

The pungency of the odor given off from fermenting 
substances is no indication of the quantity of ammonia 
liberated. Many agricultural writers give Dr. Yoelcker 
the credit of having made this discovery. The value of 
the Doctor's experiment consists chiefly in following out 
the detail of a principle, the credit of which is entirely 
due to Baron von Liebig. It is no new information to 
the agricultural world to be told that decaying animal 
substances, in addition to eliminating ammonia, also give 
off " sulphuretted and phosphurett£d hydrogen^ and a great 
variety of gaseous matter s^''^ to which the pungency of odor 
referred to is due to a very considerable extent. But it is 
quite novel that agricultural writers should deduce from 
Dr. Voelcker's researches that manures may be exposed on 
the surface of a soil without loss, and especially because 
his analyses show with great clearness the loss that must 
necessarily arise from drainage by water, on account of the 
great solubility of some of the compounds. In comment- 
ing on the analysis of drainings from a dung-heap, he says : 

" It will be seen that these drainings contain a good deal 
of ammonia, which should not be allowed to run to waste. 

"They also contain phosphate of lime. The fermenta- 
tion of the dung-heap brings a portion of the phosphates 
contained in manure into a soluble state, and enables them 
to be washed out by any watery fluid that comes in contact 
with them. 

"Drainings of dung-heaps are rich in alkaline salts, 
especially in the more valuable salts of potash. 



ADDENDA. 255 

"By allowing tlie washings of dung-heaps to run to 
waste not only ammonia is lost, but also much soluble or- 
ganic matter, salts of potash, and other inorganic sub- 
stances, which enter into the composition of our crops, 
and which are necessary to their growth." 

The Mark Lane Express^ of London, republished an 
article, by an American writer, containing the following 
language : — 

'' * Those who imagine,' says the editor of the Working 
Farmer^ 'they find good results from spreading of the 
manure on the surface, and leaving it for days, weeks, or 
months, before it is ploughed under, mistake the action of 
the litter or longer portions of the manure as a mulch for 
the action of the manure on the soil.' We so far differ from 
this and kindred opinions on the subject that we think 
manuring on the surface, for ninety-nine farmers in a hun- 
dred, the best general method of application." 

The author quoted, edifies his readers by saying, " we 
think manuring on the surface, for ninety-nine farmers in a 
hundred, the best general method of application." Nor 
does he favor us with any other rationale than his sage 
thought ! 

One very serious error has been caused by the recent 
discussions on " Farm-yard Fertilizers." Impressions have 
been made on the minds of many farmers that science at 
last has discovered that the ordinary system of treating 
farm-yard manure is correct, whereas the experiments of 
Dr. Yoelcker, which gave rise to the excitement both on 
the other and this side of the Atlantic, do not go to prove 
any such result. Many of the agricultural journals of 



256 ADDENDA. 

Europe and America, wliose editors desire to cater to pre- 
judices, were higbly pleased to liave an opportunity of fur- 
nishing such material as would delight a certain class of 
readers, and be the cause of exciting the advocates of oppo- 
site views to action. 

There is no doubt that portions of manure spread on the 
surface of a soil are washed into it. The quantity carried 
into the soil by the soluble and mechanical action of water, 
will be governed by its composition (whether clayey or 
sandy) and its mechanical condition. It is also admitted 
by the wisest advocates of the foregoing, that many and 
large amounts of the elements essential as food for plants, 
are carried to the lowlands in obedience to the same laws 
that cause alluvial deposits. 

In direct opposition to these well known truths, a writer 
in the Edinburgh Journal of Agriculture furnishes the ex- 
tract given below, which has been published in almost 
every agricultural paper in the United States. Care has 
been taken to say that the "striking experiments" were 
made by a scientific man, and by certain explanatory quali- 
fications to give more importance to the man than to the 
subject. 

If the experiments be striking, it is because they appear 
very unceremoniously to strike Dame Truth in the face. 
The writer in the Edinburgh journal says : 

" There being a difference of opinion among scientific 
men regarding the advantage of spreading dung upon the 
surface, and leaving it exposed for some time before cover- 
ing it in, Professor Legnitz, of Eldena, had recourse to ex- 
periment for the solving of the question. For this purpose 



ADDENDA. 257 

lie selected two and a half roods, which he divided into four 
equal parts. To No. 1 no manure was given, No. 2 re- 
ceived about two tons of farm-yard dung, which was spread 
immediately and covered in by means of the plough. No. 3 
was treated in the same manner, with this difference, that 
the hoe was used instead of the plough. 

" The same quantity of dung was carried to No. 4, and 
allowed to remain spread for three weeks on the soil before 
being covered in by the hoe. On the 10th of October the 
four lots subjected to experiment, were sown with about 
ninety -five pints of rye-seed each. The following are the 
total results of the crop of each lot, grain and straw included : 

No. 1 produced . . . 583 lbs. 

No. 2 produced . . . 770 " 

No. 3 produced . . . 818 " 

No. 4 produced . . . 935 "» 

The author of the above has well said, that one experi- 
ment should not be considered conclusive, and we will 
suggest that he might have added, especially because the 
full conditions for a useful experiment were not present, and 
such as were, not recorded in a manner to be of value. 

In the first experiment no manure was used, nor does it 
appear that the soil was ploughed, and as might be expected, 
it gave the smallest crop. 

In the second experiment, manure was used, and the soil 
was ploughed in the act of covering it, and, as was reason- 
able to expect, the crop was larger than in the first-named 
instance. 

In the third experiment an equal quantity of manure 
was given to the same surface of soil, but instead of 



258 ADDENDA. 

ploughing it under, a hoe was used to cover it, which gave 
the soil more mechanical disturbance than the plough ; the 
latter turns the soil over in masses, whereas the former acts 
with greater intensity, and on small quantities of soil during 
its vigorous action, thus abrading the surfaces of particles 
more fully than could be accomplished by one ploughing, 
for which reason there was a greater amount of plant food 
liberated, and as might be anticipated, the crop was larger 
than in the case of the second experiment. 

In the fourth experiment, and to which the others are 
merely introductory, the result is such as clearly indicates 
unusual conditions, such as the manure, perhaps, being so 
fermented before its use as to present a large proportion in a 
soluble condition, its application followed in all probability 
by heavy rains and dews, while the long undecomposed por- 
tion remaining on the surface of the ground for three weeks, 
acted as a mulch, and probably during such a state of the 
atmosphere as to produce its greatest action as su(3h, and 
when evenly ploughed in, the same ploughing that turned 
under the mulch, mixed the soil through which the fluid or 
manurial portions had previously been well disseminated. 
The chemical conditions of the soil may have been more 
favorable than in either of the other three experiments. 

No account is given of the condition of this soil as com- 
pared with the others, for a second crop, nor of the kind 
of weather occurring during the three weeks referred to. 
If the experiments were made during a season of drought, 
the effects would not have been such as are stated; or during 
a season of excessive rain on soil not previously disturbed, 
no such result would have been produced. It is quite com- 



ADDENDA. 259 

mon to see tall grass wliere an old plank or rail has covered 
it for a time, whicli, acting as a mulch, causes the growth 
of better grass than would have been produced by an ordi- 
nary quantity of manure, but to no small extent evidently 
at the expense adjacent of grass. The portion so mulched 
receives and fixes a larger quantity of fertilizing gases from 
the atmosphere. We are not told whether the soil used for 
the fourth experiment was or not on a lower level than 
the surrounding soil on which the others were made, and 
thus benefited by water flowing from No. 2 and No. 3, said 
water carrying elements of their fertilizers and soil to No. 4. 
Nor is it stated that the manure in each case was alike in 
quality. Indeed, the account is altogether too inaccurate 
to be reliable, and therefore should not have been published 
without comment in the most important agricultural jour- 
nals in England and America. 

Let it not be forgotten that the fluid portions of manure 
are highly valuable ; the various salts they contain are in 
a state of solution, and are capable of extreme division, in 
addition to assisting by their presence all the sui generis 
actions of a chemical character which take place in a soil ; 
for just as yeast multiplies itself in a brewery by its action 
on vegetable matter, so do the constituents in solution in 
the urine of animals induce chemical changes which cause 
the integrants in the soil to be rendered suitable jmbulum 
for plants. 

From the foregoing it must be evident that the excre- 
ments of all animals should be well cared ; and their mani- 
pulation should be such as not only to secure their con- 
stituents for the use of plants, but to change the condition 



260 ADDENDA. 

of such of them as plants cannot avail themselves of, by the 
usual treatment of the manure before it reaches the field. 
In addition to the inorganic matter, are many proximates, 
known as organic compounds, which plants may use, and in 
a condition which renders them active in the further decom- 
position of a soil for the use of plants. Among these are 
the bile and chyle of the animal, and the different vegetable 
proximates not appropriated ; and we are sorry to say that 
most farmers, by the injudicious management of manures, 
lose them by evaporation, washing, etc., and also much of 
the more valuable and most soluble of the inorganic consti- 
tuents. These occur in open farmyard practice, and in the 
washes and streams that pass away, sometimes crossing 
roads, on their way to creeks and rivers, while from the 
exposed surface ammoniacal and other gases, hurtful to the 
health of animals, pass into the atmosphere. 

Some of the losses that arise from improper exposure 
are as follows : 

The most soluble elements, and consequently the most 
readily available constituents to plants, are washed out by 
rains. If the manures permeate the farm-yard, a larger 
amount of surface is exposed to evaporation than if 
gathered into a heap. 

The amount of surface exposed to evaporation is a great 
number of times increased if cattle are permitted to roam 
promiscuously through the yard. Every step taken by an 
animal exposes a new surface to the action of sun and air. 
Every spear of hay or straw projecting from the surface of 
manure, by capillary attraction, gives an increased amount 
of surface for evaporation. 



ADDENDA. 261 

The proper composting of fertilizers is, to American far- 
mers, of more importance than to the English cultivators of 
the soil : because gases from any decomposing substance, 
whether animal or vegetable, cannot so readily pass into an 
atmosphere like that of England, Ireland, or Scotland, as 
they will into that of America, owing to the sudden changes 
of temperature of the latter. 

Any vegetable matter that can be decomposed in a com- 
post, should not be burned. It is not proper, therefore, to 
subject witch or couch grass, clippings of hedges, or live 
fences, leaves, or other similar materials, to the action of 
fire. They ought rather to find their way to compost 
heaps, and receive such treatment as will secure full de- 
composition. Let everything of a manurial character find 
its way to the compost. Remember the Scotch adage: 
" A stone is the only mote in a muck heap." 

Such adages, now being published in so many of the 
agricultural papers, that " No one should have a farm-yard 
bigger than the body of his ox-cart," are mere words with- 
out meaning. It would be well for the authors of such 
sayings to give accompanying explanations. One-sided, 
prejudiced views never lead to truth ; writers should not, 
Paganini-like, play on a single string. 



LAND DRAlKAaE. 



There can be little doubt that thorough drainage is one 
of the surest means of preparing the soil for the applica- 



262 ADDENDA. 

tion of the principles so ably set forth by Baron von 
Liebig. 

We have no space to devote to the history of this impor- 
tant subject ; there is, however, little doubt that improve- 
ments in the art of drainage, extending over a long series 
of years, show conclusively, the applicability of thorough 
land drainage to a large proportion of our continent. Its 
advantages are very numerous, a few of which may be 
briefly stated. Its object is not merely, as many suppose, 
to rid the land of stagnant water. The action of the air on 
the soil, and the absorption of moisture from it by the 
driest lands that are under-drained and deeply cultivated, 
are advantages that are now well considered by the intelli- 
gent practical farmer. Soils, especially such as are full of 
stagnant water, treated in this way, are easily worked, 
when the water is carried away by under drains ; and this 
is particularly true of them when sufficient time has 
elapsed to permit those important influences of the air 
which liberate pent up food, and thus improve its physical 
condition, thereby lessening the labor necessary for their 
successful culture. Under-draining, even without the appli- 
cation of manure, has been known to double the crop in 
many soils. Let it not be forgotten, however, that in this 
point of view, it aids the "rapid system of spoliation," 
unless the farmer restore to the soil the elements taken 
away by crops. In under-drained soils, when the drains 
are at full depth, the roots of plants can strike deeply in 
search of food ; thus they are invigorated and not likely to be 
thrown out or "winter-killed" by frequent freezings and 
thawings, or summer-killed by not having a deep soil 



ADDENDA. 263 

in which to luxuriate and absorb the moisture which is 
sure, in the hottest weather, to be deposited on the 
cool particles. It is also well known that under-drained 
soils are warmer than those full of cold stagnant water. 
They are earlier in spring and not frozen till later in the 
fall, thus giving the farmer a longer season in which to do 
his work. What can be more uninviting than a cold, wet, 
unproductive soil? "Can the rush grow without mire? 
Can the flag grow without water ?" After thorough drain- 
age, the rush and the flag disappear, and instead of coarse 
grasses, alders, skunk cabbages, mosses, and other rubbish, 
fine plants may at once be grown. 

Into low, wet places much of the fertility of the higher 
lands is washed by the soluble and mechanical action of 
water, which is made available by thorough drainage, and 
a basis is thus laid for all possible improvements of the 
soil. 

Although the farmer who can buy new and rich soil at 
a very low price, is not likely to under-drain it, because he 
can buy more land at little cost, which, although studded 
with stumps, that will yield him full crops of cereals ; still 
few will doubt that thorough drainage is applicable to 
extensive tracts of land near large cities, used for agri- 
cultural purposes. Indeed that the farmer must drain 
all such lands that are wet, or do without crops, few will 
doubt. 

George W. P. Custis, Esq., at the meeting of the United 
States Agricultural Society, in 1857, asked attention to 
100,000 acres of rich land, on the banks of the lower Poto- 
mac, now lying waste, but which if thoroughly drained, 



264 ADDENDA. 

might at once be rendered available for tlie production of 
the jfinest crops. This is only one case among many 
beyond number which must yet yield to the almost magic 
influences of thorough drainage as the agricultural resources 
of our country are developed. A wide field for opera- 
tion offers itself in the fifty million acres of swamp land 
granted by Congress to different states during the past ten 
years, with the hope that their governments will reclaim 
them. Many a farm, by the drainage of low places, would 
add quite a number of acres which have received the wash 
of the highlands for ages, capable of immediate cultiva- 
tion and profit. 

The drainage of the Central Park, under the direction of 
George E. Waring, Jr., Esq., is probably the most thorough 
work, on a large scale, that has yet been done in this coun- 
try. Enough of this is already done to see to some 
extent its efficacy ; although the drains have not yet been 
long enough made to act in the best manner, still the water, 
clear as crystal, may be seen gushing from the almost 
magical pipes. On the land appropriated for the park, 
there were many offensive pools, half full of decaying 
vegetable matter, whose value, as a manure, to other parts 
of the grounds, would more than pay the cost of drainage. 
As the park consists of a great variety of soil, among 
which may be named both blue and yellow clay of the 
most tenacious kind, there is a fine opportunity for seeing 
the effect of tile drainage by farmers who may visit the 
grounds. 

The first thing to be done in the laying out of drains is 
to understand the natural lay of the ground, selecting the 



ADDENDA. 265 

lowest part, having the best outlet, as the line for the main 
drain. The lateral drains should connect with the main at 
the same angle as the slope of the ground to the line of the 
main. Where the slope is not sufficient to give a self-evi- 
dent fall it will be necessary to have the ground levelled by 
an engineer, as any inaccuracy in this respect would be 
fatal to the efficient working of the drains. The engineer 
proceeds by driving stakes, of two or two and a half feet in 
length, in the ground at given intervals along one of the 
intended sides of each drain, and they are lettered and 
numbered for easy reference. Beside each of these stakes, 
a shorter one is driven, the top of which should be a little 
above the ground, so as to be easily seen. On the shorter 
stakes the engineer's rod is placed as occasion may require, 
when observations are made to ascertain levels. After the 
calculation of the grades, the depth of the intended excava- 
tion, from the top of the shorter stake, is marked in feet 
and tenths on the longer one. 

It is wel] to sound the lines of the drains with a sound- 
ing-bar, to ascertain whether rocks, separate stones, boul- 
ders, etc., will much interfere with the cutting of them ; in 
which case new lines would have to be found. The obser- 
vance of this precaution will save a great deal of labor and 
expense. A sounding-bar is a round iron rod about an 
inch thick and five or six feet long, tapering towards the 
point and enlarged at the head to about two inches in dia- 
meter; having a cross-bar about eighteen inches long through 
an eye in the head. Sounding-bars three-quarters of an 
inch thick, and seven or eight feet long, are sometimes used; 

but they have to be worked into the ground by a swinging 

12 



266 ADDENDA. 

motion of the hand. This is a very slow process, compared 
with the speed with which the larger sounding-bar may be 
driven into the ground by a sledge. Twenty soundings 
may be made with the larger bar, while one is effected with 
the smaller one. 

The main drain and laterals being located, commence 
digging at the outlet of the main, and so proceed to the 
head of the drain — that is its most distant part from the 
outlet. Care must be taken to give them a regular and 
sufficient fall, which should not, if possible, be less than one 
foot in 100. A uniform grade on the bottom of the drain 
is very desirable ; and it is for this reason that levelling-rods 
are used. A levelling-rod is shaped like the letter T and is 
made of board about one inch thick, five or six inches wide, 
with a piece of board of same width about eighteen inches 
long nailed across the top, and square to, that is at right 
angles with, the perpendicular. All the rods must be the 
same length ; otherwise a uniform grade cannot be obtained. 
Levelling-rods are usually made six or seven feet long. 

Having got the drain as nearly as possible to the required 
depth, place the rods on the bottom of it in an upright posi- 
tion about forty feet apart;, then hold another rod, which 
may be lighter, on the bottom of the drain, and if its grade 
be correct, the top will lie in a line with the tops of the 
other two. Great care must be taken not to go below the 
proper grade, as in that case the bottom of the drain will 
have to be filled, and cannot be made as compact as the 
natural bed. Where it is necessary to have the land lev- 
elled by an engineer, and the fall is only sufficient, the rods 
must be placed very accurately at the depths- — calculated 



ADDENDA. 267 

from the " levels" — which are generally marked on stakes 
at proper distances along the lines of the drains. Beside 
each stake, so marked, is the grade stake, the top of which 
is a fixed point from which to measure the depth of the 
drain. In order to find the exact depths of points along 
the bottom of the drain corresponding to the depths marked 
on the stakes, a sliding measure is used having a plumb- 
line attached. First ascertain the required depth from the 
top of the grade stake to the bottom of the drain ; then 
apply the sliding measure, the arm set to the proper height. 
K the bottom of the drain be soft, place a flat stone under 
the end of the sliding measure, making due allowance for it 
when removing the soil from the point where the levelling 
rod is about to be set. The sliding arm of the measure 
must rest on the top of the grade stake. When the proper 
depth is thus ascertained, remove the measure and place 
the levelling-rod upright on the stone, it being held in its 
position by a board reaching across the drain having a slit 
in its centre into which the levelling-rod is wedged. 

The main drain dug and graded, then proceed with the 
laterals, commencing with those nearest the head of the main 
and proceeding on to those nearest the outlet. Commence 
to lay the tiles first in the main drain, and continue a little 
beyond the point where the highest lateral connects. Pro- 
ceed in the same way with the rest of the laterals, laying 
the tiles connecting with the main, and then place inverted 
sods, if the soil be silty, and cover with soil to the depth of 
a foot and a half, and use a pounder to compact. Every 
foot of soil put in afterwards should be pounded. These 
precautions will prevent water in case of a rain storm from 



268 ADDENDA. 

rushing rapidly through, before the soil has become settled ; 
on the contrary it will pass gradually without carrying any 
silt into the tiles. Continue to dig laterals and lay tiles in 
the main and in them as fast as dug until the outlet of the 
main is reached. 



INDEX. 



PAGE 

Absorbent power of soils varies 28 
Agricultural Colleges system of 
instruction in, 
defective. . 209 

— — the cause of the 

present conflict 
about princi- 
ples . . 210 

— instruction, how ac- 

quired . .12 

— prize questions . 16 

— teachers, errors of . 161 
Agriculture, based on expe- 
rience . . 2 

— connection with 

chemistry . . 4 

— false teachers of . 11 

— modern, deficient in 

principles . .187 

— present system of, 

not rational . 20 

— spoliation system of 144 

— spoliation system 

of, in America . 144 
Agriculturist, the empirical, a 

trader . .138 

— the scientific du- 

ties of . . 140 
Air, carbonic acid and ammonia 

in 69 

America, exhaustion of soil 

in ... . 144, ni 
A.mmonia, action of, compared 

with that of water 165 

— amount of, in air . 69 



PAOB 

Ammonia, combbaation of, with 

soils . .110 

— effect of salts of, 

attributed to the 
nitrogen . , 43 

— effect of salts of, 

on production of 
straw and leaves 80 

— exhaustive action 

of salts of . .67 

— experiments with 

salts of, at Bogen- 
hausen . . 44 

— in a soil, not a sign 

of its fertility . 59 

— quantity of, in 

soils . 59, 169 

— quantity of, no cri- 

terion of produc- 
tiveness . . 59 

— salts of; double ac- 

tion of, in soils 52, 16*7 

— solvent action of, 

on earthy phos- 
phates . . 48 

— without mineral 

matters, of no use 
to plants . . 88 
Aramoniacal manures, when 

useful .... 98 

Annuals, absorption of food by 71 

Apatite 96 

Appendix . . . .221 

Arable soils, how formed . 119 

Ash constituents . . .116 



270 



INDEX. 



B. 



Bavaria — experiments of agri- 
cultural society of) with am- 
monia . . . .60 
Beet — minerals removed by .182 
Birkenfeld peasant, his opinion 

of clover . . . .160 
Block, Albrecht, opinions of . 141 
Bogenhausen experiments with 

salts of ammonia, &c. 44 
— experiments with 

nitrate of soda, 41 
Bog-water, analysis of . .36 
Bone earth, comparison with 
Chih-saltpetre . . .173 



C. 



Carbonic acid, amount of, in air 69 

— — source of . .70 
Cato, opinions of, on agriculture 190 
Cattle, stock of, not necessary . 198 
Cereals, amount of nitrogen in 74 
Chemistry, connection of, with 

agriculture . . 4 

— elementary instruc- 

tions in . .206 

— reaction against . 5 
Chili-saltpetre, effects of, . . 47 

— — solvent action of, 

on earthy phos- 
phates . . 48 

— — comparison of, with 

guano and farm- 
yard manure . 162 

— — exhaustive effects of 67 
China, continued fertility of 

land in . . . .204 

Chinese, agriculture of . . 200 

— mode of collecthig 

human excrements ib. 

— mode of sowing wheat 202 

— valuation of human 

excrement . . 201 
Clover, introduction of into 

Germany . . 155 

— and corn, relation of, to 

each other . . 149 



Clover, and potatoes, phosphoric 
acid and 
potash re- 
moved by 103 
Columella, opinions of, on agri- 
culture . . . .189 
Combustible matter of plants 

derived from air . . .110 
Common salt, effects of . 43 

— — experiments with, 

at Bogenhausen . 44 

— — solvent action of, on 

earthy phosphates 48 
Compensation, the law of . 205 
Corn, mineral matters of, lost 

to the land . .150 

— and flesh, mutual rela- 

tion of the production 
of . . . .199 
Crops, rotation of . . . 142 



D. 



Deep rooting plants, effects of 105 
Disintegration of rocks . .122 
Distilleries, residues from 169, 180 
Drainage water, ammonia in . 34 
— — analysis of .31 



E. 



Earth, outer crust of, conden- 
ses and retains the food of 
plants 40 

Earthy phosphates rendered 
soluble by salts of ammonia, 
common salt, and Chili-salt- 
petre 48 

Excrements of man, amount of, 
in large towns . . .176 

Exhaustion of soils, law of . 94 
— — — real nature of 108 

Experience of practical men as 
a guide .... 120 



Fallow, effect of 
False reasoning 



98 
121 



INDEX. 



271 



PAGE 

False teachers . . . .11 
Farm-yard manure . . .109 
— — value of . Ill 

Fertility, duration of. propor- 
tional to amount of 
mineral matters in 
soils . . .61 

— how maintained . . Ill 

— not restored by or- 

ganic matters . .110 

Finger and toe disease . . 84 

— — removed by lime 84 

Food of plants absorbed in 

proportion to 

root surface . 10 V 

— — — atmospheric 

and mineral . 21 

— — — not in solution 

in soils . 30 

— — — not received 

from a solution 87 

— — — rapidity and 

duration of ac- 
tion of . 22 

— - — — relation of 

phosphates 
and nitrogen 
compounds in 170 
Formula for the chemical truths 
in the agricultural letters . 264 



G. 



German agriculture before the 

Thirty Years' War . .153 
Graham — analysis of waters by 31 
Grain, conditions for producing 

largest crops of . . 101 

— decrease in the condi- 

tions for its growth . 101 

— increase of, by means of 

straw constituents . 99 

— and straw unequal de- 

velopment of . .100 
Grasses, underground growth of 

71, 224 
Green crops, effects of . .77 

— — thrive without ni- 

trogenous ma- 
nures . . 77 



Green manures, effects of 


PAGE 

89 


Guano, comparison of, with hu- 




man excrements 


177 


— effects of^ not due to its 




ammonia alone . 


168 


— experiments with . 


60 


— nature of . . . 


133 


— not a complete substi- 




tute for human ex- 




crements . 


182 


— quantity of, imported . 


179 



H. 



High farming, a rapid system 

of spoliation . . . 148 

Highwayman, on the Ehine, 

system of .... 156 
Hofmann, analysis of water by. 31 
Hoskyns, opinion of . . 9 

Human excrements, collection 

of from towns . . .217 
Humus, when useful . . 42 

— former belief in the 

value of . . .41 
Huxtable, observations of .57 



Inductive method applied to 

agriculture . 8 
— — triumphs of 8 

Irrigation, effect of, on injurious 
organic matter . . .85 



K. 



Krocker, analysis of drainage 
water by . . . .32 

Kuhlmann, experiments with 
salts of ammonia by . .61 



L. 



Land, cause of unequal pro- 
ductiveness of . . .66 



272. 



INDEX. 



PAGE 

Lawes, experiments of, with 
ammonia and mineral 
matters . . .42, 61 

Leaf-surface, effect of on 
amount of nitrogen absorp- 
tion .... 16 

Leguminous plants, amount of 
nitrogen in . . . . H 

Lemna trisulca, analysis of ash 
of 36 

Lime, a cure for injurious 
organic matter . . .85 



M. 



Manures, effect of, on land, 
how properly es- - 
timated . .1*13 

— failure of supply of 183 

— nature of . .108 

— nitrogen of, derived 

from air . .7*7 

— not always food for 

plants . .55 

— proper supply of . 82 

— proportion of phos- 

phates to nitro- 
gen in . . 172 

— value of, estimated 

by nitrogen pre- 
sent . . .170 
Maremma . . . .271 
Meadows, vegetation of, depen- 
dent on underground suckers 72 
Mecklenburgh, agriculture of .157 
isniler, analysis of waters by . 31 
Minas Geraes, agriculture of . 148 
jMiueral food, all elements of, 

possess equal value . . 20 
Mineral matters, activity of, in- 
creased hy salts 
of ammonia, Chili- 
saltpetre, &c. . 65 

— — importance of, in 

Lawes' experi- 
ments . . .61 

— — necessary to ani- 

mals . . .114 

— — in soils not inex- 

haustible . 116, 130 



PA6B 

Mineral matters, restoration of 124 
Moisture, attraction of soils for 38 

— condensation of, in 

soils attended by 
evolution of heat . 39 

— supply of . . .40 
Molasses, residue from, used as 

manure .... 169 
Mud from pools, &c., a fertilis- 
ing agent . . 37 
_ _ _ effects of . .165 



N. 



Nitrate of ammonia and 
common salt, experiments 

with 47 

Nitrates, effects of, on ci'ops . 43 
Nitrogen absorbed in propor- 
tion to root surface 58 

— compounds and phos- 

phates, relation be- 
tween . . . 113 

— in different crops . . 74 

— supposed loss of, in 

rotten manure . .131 

— the supposed active 

ingredient in salts 

of ammonia . . 42 

— theory of manures 

115, 170 
Nitrogenised products in plants 

proportional to leaf surface . 76 
Nitrogenous manures for cereals 74 

— manures when use- 

ful . . . 81 

— manures, effect of, 

on plants with 
large leaves . 76 
Nutrition of plants, present view 
of 24 



0. 



Oats, remunerative crop of . 94 
Offenbach, Green Doctor of .12 
Oil mills, residue from . .180 
Organic matter, not a source of 
fertility in itself . . .118 



INDEX. 



273 



PAGE 

Organic substances destroyed 

by irrigation . 85 

— — destroyed by lime 85 

— — in soils frequently 

a cause of dis- 
ease . . 84 

— — not exhausted by 

cultivation . 110 

— — when useful in 

soils . . 74, 16 



P. 



Perennials, absorption of food 
by 11 

Phlogiston . . . .197 
Phosphoric acid, in what forms 

present in soil 96 

— — not present in 

drain, river, or 
well water . 34 

— — quantity removed 

by clover and 
potatoes . 102 

Phosphate of lime, action of soil 

on . . .25 

— — — how distributed 

through soils . 97 
Phosphate of magnesia, action 

of soQ on . . . .25 
Phosphates, loss of, by the 

soil . . .176 

— removed by potatoes 102 

— and nitrogen in 
food . . .171 

Plants, amount of nitrogen 

in . . . .74 

— conditions of the life of 21 

— general constituents of 

ash of . . .20 

— deep and shallow root- 

ing, object in cultivat- 
ing . . 104, 152 

— mineral constituents of, 

not received out of a 
solution . . 30 

— nutrition of . .22 

— origin of combustible 

portion of . .20 



PAGB 

Plants, possess a power of se- 
lecting food . 35 
— present view of mode 
of nutrition of, 
erroneous . . 24 
Pliny, opinions of, on agricul- 
ture 193 

Potash in plants and drain water 

compared . . 33 

— removed by beet and 

potatoes . . 182 

— salts rapidly decom- 

posed by soils . 52 

— and soda salts diflfer- 

ently acted on by 
soils . . .52 

Potassium, chloride of, action of 
soil on .... 26 

Potatoes, minerals removed by 182 
— phosphoric acid re- 
moved by . . 102 

Poudrette, relation of phos- 
phates to nitrogen in . .172 

Practical agriculturists, their 
sensibility to opposition . 18 

Practical instructions, to be 
always preceded by theoreti- 
cal 207 

Practical teachers, false reason- 
ing of 127 

Prize questions in agriculture 
valueless . . . .17 

Progress based on experience, 
limited .... 4 

Pusey, opinions of . . .5 



R. 



Remunerative crops, how de- 
termined . . . .93 
River water, analysis of . .31 
Rocks, disintegration of . .122 
Rome, the cause of the exhaus- 
tion of the lands of the 
ancient world . . .185 
Roots, absorbent surface of . 58 

— action of, on stones . 35 

— protected by the action 

of the soil ... 83 



274 



INDEX. 



Rotation of crops, without re- 
storation of minerals, 
ultimate effects of . 143 
— value of . . . 143 
Rye, remunerative crop of .93 



S. 



ScHATTENMANN, experiments 

with ammonia . . .60 
Schubert, Knight of Cloverfield 155 
Science confers power . . 6 

— the objects o^ in agri- 

culture . . .211 

— the results already ob- 

tained by . . . 215 

— true province of . .6 

— value of, recognised . 9 
Scientific research, true mode of 15 

— teaching, rejection of 14 
Silicates, how distributed 

through soils . . .97 
Soda, nitrate of, effects of 52, 55 

— — — experiments with 47 
Soda salts only partially de- 
composed by soils . . .53 

Sodium, chloride of, action of 

soils on . 26 

— — effects of, on 

crops . . 43 
Soils, action of, on solution of 

chloride of.potassium . 26 

— action of, on eolution of 

chloride of sodium . 26 

— analysis of, in Prussia . 116 
" — attraction of, for moisture 38 

— cooled by evaporation . 39 
effects of, on solutions "of 

ammonia, potash, phos- 
phoric, and silicic acids 
limited . . .28 

— effects of, on solutions of 

salts indispensable to 
plants ... 25, 26 

— effects of, on solutions of 

salts not indispensable 

to plants . . .25 

— eight elements required 

by plants iu . . 23 



Soils, exhaustion of, by removal 
of minerals without re- 
storation . . .67 

— fertility of, dependent on 

quantity of soluble 
mineral matters present 65 

— fertility of, not dependent 

on nitrogen or organic 
matter . . .118 

— mechanical division of . 89 

— mineral matters of, in- 

soluble in water . . 25 

— productiveness of, how 

estimated . . .90 

— progressive exhaustion of 103 

— rich in organic matter, 

effect of . . .29 

— warmed by absorbing 

moisture , . .39 
Special law .... 7 
Stercutius, god of manure . 155 
Subsoil, food derived from . 104 
Suckers, underground, import- 
ance of .... 72 
Sulphur compounds and phos- 
phates, relation between . 114 
Sulphur and nitrogen organic 
compounds . . . .113 



T. 



Temperatuke of soils, elevation 
of, by condensation of mois- 
ture 40 

Thames water . . . .31 

Theory 7 

Theoretical and practical teach- 
ing, not useful together . 207 
Thomson, observations of. . 57 
Tobacco, minerals removed by 183 
Trader, the objects of a . . 3 
Turnip, finger and toe disease 
in 84 



Varro, opinions of, on agricul- 
ture 192 



INDEX. 



275 



Yine-dresser, his mode of im- 
proving his soil . . .184 
Yines, exhausting to land . 154 
Yirgil, opinions of, on agricul- 
ture 192 



W. 

Walz on the causes of fertility 

in a soil . . . 135 

diminution of volume 

of soils . . . 126 

disintegration of rocks 122 

exhaustion of soils . 123 

guano .... 134 

the loss of nitrogen in 

manure heaps . .131 



PAGK 

Walz on the nature of manure . 135 
the necessity for pro- 
ducing manure . 129 

— opinions of, on arable soils 122 

— on the restoration of 

minerals . . .124 

— on the value of fresh manure 133 
"Water plants receive food from 

solution . . . .35 
Waters, river and well, analysis 

of 31 

Way, analysis of drainage water 

by .... 32 

— observations of . . .57 
Wetterau, farmer . . .159 
Wheat-field, when exhausted . 93 
Writers on practical agriculture 121 



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